I'm curious as to why this is needed? I don't really see a reason why the full credits is needed for a 3 min or less speedrun.

If there is something in the credits that you check for, and that is why it is required, then by all means I'd love to be educated.

I would assume it's because the credits display total games played at the end and this number should be consistent with the route used for the run.

That's kinda dumb. That's like saying "okay we see you did the run...but did you actually do it? Let's see the number at the end. That will prove you did this run legit"

I just fail to understand what this rule could possibly accomplish, unless I'm not seeing it.

For a full game run I can see a rule like this..

For a 3 min speedrun? It ain't that important where recording over 10 min. of credits is absolutely detrimental for my run to be considered legit.