I have since had another look. Lee Anderson was in power (as a Conservative), and abstained from https://votes.parliament.uk/votes/commons/division/1416#notr... – though I'm not sure what this vote was actually on, and this doesn't support my original claim (that Reform MPs voted in favour of the Online Safety Act). Perhaps someone with more understanding of British Parliamentary Procedure could look through the relevant votes and see whether my claim was actually correct.
Also, since there were zero "No" votes from Tories, it could be that the party whip imposed conditions on Tory MPs.