After looking some more, I think the new moto may be related to the 2019+ fuel injected crf110 motor, and not related to the OG/SF grom motor. That would mean max bore sizes of 56mm which gives a capacity of 155cc with the new stroke. Look at these comparison shots of the stator covers of the 21 grom and the 20 crf110. I could be wrong, but we'll have to wait and see.
View attachment 88574
View attachment 88575
crf 2021 engine still the old msx-monkey -cub-ct-wave .