Lower spec bike - way more difference than expected but what is the biggest cause?

Thats not the reading I’ve been doing.

The issue is the 11 speed hub is 1.85mm longer than the 10. On the R7000 cassette there should be a 1.85mm recess at the back of the largest sprocket. To fit r7000 on an 11 speed hub you should always need a spacer… at least from my reading. I’ll be putting it to the test myself soon enough.