Laws of chess:
"B.1
A ‘blitz’ game is one where all the moves must be completed in a fixed time of 10 minutes or less for each player; or the allotted time plus 60 times any increment is 10 minutes or less."
https://handbook.fide.com/chapter/E012018
So yes: 10|0 is blitz and this site erroneously considers it rapid.
All time controls seem much shorter otb... You can do more moves online than otb in 10+0, which could make it rapid instead of blitz...




I found that the opposition was worse in 10/0, even when it was still blitz, meaning that seperate sets within the blitz format had ratings that meant different things from each other. It could be that's why they changed it.