I wonder why it was so different at EBI-
A few reasons. When points are involved, grapplers are less likely to go allow themselves to be swept or passed. Gordon Ryan for example loves to allow people to mount him so that he can frame on the hips, enter ashi garami, and get the outside heel hook. Now maybe he would totally allow himself to get mounted to go for that transition in a points match, but I think he would at least be more hesitant to do it. I mean one can make a very strong case that being mounted in a no gi sub only match can actually be better for the bottom player if they're an ashi/slx specialist.
There is also less of a tendency to go for sacrifice subs in points matches. Let's say someone working to pass the guard and they lock up guillotine choke, darce choke, kimura lock, or a toe hold. They are less likely to go to the bottom in order to finish it if points are involved, because not finishing the sub will give you a strong chance of losing. Eddie Cummings said that almost word for word in a polaris pro preview video on youtube.
Also, certain positions themselves are harder to come by. The RNC is the most common submission in mma and it's always the most common choke (if not sub) at adcc and nogi worlds. Many people open up their back when punched in mma and many people open up the back when they are getting their guard passed in points matches. Because they turtle up to not get scored on. In sub only a lot of grapplers elect to eat the guard pass and work to re guard instead of exposing their back. That's why you don't see that many RNCs at ebi outside of overtime.
Darragh O'Connail was interviewed after he north south choked Boogey Martinez at EBI and he said he worked on that instead of his usual favorite guillotines/darce series because he knew less opponents would turtle during his guard passes. He's competing again at EBI 11 next weekend.
Also an event like adcc is done over a weekend. EBI is done in one night. So a grappler in the semi finals at adcc is going to be much more rested after a full night of sleep after their first two matches than a grappler in the semi finals of EBI. This will likely change their strategy, and it will definitely increase their chances of getting swept/passed/back taken/submitted due to fatigue alone.