>>12610592She really is. Korone works out and boxes as a hobby though so she is in shape, while Okayu is just a gamer streamer so she was not. She may be in better shape now that she was made to become an idol (which she was upset about).
You can see a bit of the difference in the live they did. Korone is quicker and more agile despite being 13 years older and having a broken leg at the time (watch her knee shake when she lands) compared to Okayu's more lumbering form (watch the entire stage shake when she lands)