Could IL WRs come from Full-game runs? I was looking at the NM Any% for the ILs and comparing them to my splits and was thinking of clipping those levels via Twitch Highlighter and submit them but wanna be sure I comply to the rules

Hey, sorry it took me a while to respond. The total time on the statistics screen at the end of an individual level is a requirement for those and it doesn't exactly match the time as measured by livesplit or similar. One slight issue with that could be the rounding to full seconds, but seeing as not many people run ILs I doubt it will ever become a problem.

There are however quite a few runs submitted and verified by using the in-game time measurement so it would be unfair towards those to allow livesplit timing, so the answer is no. I don't believe it's a problem for you to run the individual levels and I'm pretty sure you would achieve better times too.