This is a style issue. Not at all on the same level. The ISO standard defines a space, but many, many style guides suggest otherwise. E.g. Very often you will find advice to omit space for one-letter abbreviations (i.e. '100g' not '100 g') — I believe this specific one is in the Chicago Manual of Style.

hey at least they're not doing something absolutely and deliberately idiotic like putting the % in front of the number like a currency symbol.

Keep being you. We all have our weird things that bother us. Apparently the spaces issue is centuries old and used a minority of the time, so you've just got a lot of convincing to do. Maybe you can multiply your effects by writing bots that, for instance, submit github pull requests. Good luck!