The main principle of ALSA design is a sort of "hot-plug".
Today, you do not need to reload ALSA, if you change .asoundrc
Though a media player may (or may not) need to be re-started.

It is self-evident. If you don't believe, read Gentoo Wiki and try proposed tests.

The problem is that ALSA is poorly documented, and, therefore, one has to use the method of trial and error to find the correct solution. However, what is correct today might be wrong tomorrow.

To foresee changes in the "advanced sound system", one may need "a deeper level of understanding of ALSA", or a sort of esoteric knowledge for navigating uncertainty.

ALSA in user space is a sort of software mixer with plugins, such as dmix, dsnoop, and the like. Many years ago, ALSA was so buggy that it was necessary to reload ALSA to enable changes in .asoundrc. Today, to enable dmix or other plugin in .asoundrc, you do not need to reload ALSA.

In 2008, it was necessary to reload ALSA to enable dmix. This problem was fixed in 2009 (or 2010) in a new version of ALSA. In 2010, Ubuntu users were advised to recompile ALSA to fix sound problems, although it was enough to remove pulseaudio. In 2010, Ubuntu users asked questions like this: "Could I remove ALSA, and use PulseAudio instead?"

It is very logical:
1. If pulseaudio is much better than ALSA, it is reasonable to remove ALSA and install pulseaudio.
2. If pulseaudio needs ALSA to work, it cannot be better than ALSA, and, perhaps, is not needed.
3. If ALSA can work without pulseaudio, it might be reasonable to remove pulseaudio as an unnecessary fifth wheel.

Today, many "computer scientists" firmly believe that Fedora Linux has PipeWire instead of ALSA. It is impossible to convince them that they have ALSA installed and working in their Linux system, because they do not want to know what ALSA is, and how it looks like. They have the gift of faith in the sense that they do not trust their senses and their ability to think. They have a special, extraordinary trust in PipeWire's promises and a sort of "supernatural ability to believe in the unseen and to act on spiritual truths despite physical evidence to the contrary".

dmix is needed to make ALSA usable.

The speexrate converter is also crappy.

In 2008, Ubuntu was infected with PulseAudio which was a replacement for dmix and ESD. PulseAudio was very advanced, but buggy and unusable. ESD was not so buggy. It was usable, and, therefore, it was deprecated. However, it was still  available, and the standard solution for sound problems was to remove PulseAudio and install ESD. The best solution for sound problems was to remove both ALSA and PulseAudio, compile OSS4 and install it.

NOTE: ESD was created, because dmix was buggy and unusable. ESD was buggy, but usable. When most bugs were fixed, it was deprecated (in 2008).

ESD was mostly using ALSA's built-in OSS emulation (alsa-oss: snd-pcm-oss and snd-seq-oss) which performed much better than native ALSA in 2008. The emulation provided a more stable solution for applications still using the Open Sound System (OSSv.3) API.

In 2008, dmix was extremely buggy (and ALSA resamplers have always been crappy). The sound quality was really horrible with dmix. This problem was fixed in 2010 with the fftrate ALSA plugin (and with ALSA update).

ALSA was designed as a universal solution to all problems, but it was so buggy that it was decided to create pulseaudio as a truly advanced solution to all problems. Pipewire was created for a similar reason.

Today ALSA is not so buggy and even usable, if it is correctly configured.

Otherwise I think one of the confusing aspects of ALSA configuration changes is that in general any program that use the audio system will end up loading an instantiating a configuration structure internally only once, when it starts. Therefore, such programs need restart after a change to the configuration source files, which include the user's .asoundrc file.

Though, a program may of course have been made to reload the configuration, and in that case such a program will do so as programmed and then rebuild the internal configuration structure from that on file.

I would suggest that old and bad documentation can only be remedied by writing new and better documentation; grumbling about what's existing and discussing it's badness is just waste of time.

This chapter was deprecated and removed from the official ALSA documentation about 15 years ago (or more). However, the true believers still believe that it is necessary to reload ALSA "for the changes [in .asoundrc] to take effect".

To believe in a dogma, one should not trust his senses and his ability to think.

EDIT:

It is so "technical", that it is almost incomprehensible.