As I said, I do not understand the limit. This is Itch specific. If other sites do it, I did not notice back when I tried to learn about this.
And if it is in an archive or if it is in another sort of archive, the assets are still taking up space and it still takes computation to extract them. So what is the difference in "quality", if you have your moving animation of a sprite as 8 files or as 8 tiles of a bigger image file or as a separate engine specific archive file that is equivalent to a zip with 8 files.
I can imagine, that it might hamper performance if there are many assets, but on the other hand I also know that these types of performance issues are a thing of the past. Or they should be. Doing things in a file system is overhead. Yes. But if the game file is transferred to the client and is not "physically" extracted, it should not matter at all, how the insides of that archive are managed.
What I also would understand, if the assets are kept on the server, and there would be network traffic necessary, including lots of headers, for each tiny asset transferred. But the way most web games load, I suspect that this is not true for most games, as they have one long loading bar indicating that all is transferred in one go.
And, well, what difference in quality/performance is there, if I have the big number of files on the client as a downloadable zip or as a web game zip in the browser's cache. Limiting file size for web games makes a lot of sense. Limiting the number of files inside that web game, I cannot understand.
What am I missing here? To me it looked like an attempt to discourage web exports from engines that are bad at this and have as a common trait that they use a large amount of files by doing some lazy export thing. Similar to a "pdf export" that is just a series of images, instead of a document.
Is there a guide for html games, how assets should be handled? Some best practice? Something that tends to output low number of files? Because if this boils down to use something like renpy does with their rpa files, we are at square one, imho, since putting the assets in a zip is already minimizing files - to one, the zip file.
There is a sticky about reduzing build size. But this talks only about size and not number of files. If number of files really is an issue, a sister sticky about reduzing files in a web build might be a good idea.