There are plenty of people that voted for one who'd never vote for the other so simply adding them together doesn't really mean anything. If the conservatives went more Conservative and got the media on soap box they would lose votes, and if Reform went full cuckservative no one would vote for them.
It's like all those people coping in 2019 that added together Labour, lib dem and green votes and then claimed they would have won rather than losing in a landslide, they're not the same party.
This was an unusual election for the fact the government was spanking away a large majority to give a larg majority to the other side, and that a new party swept in a instantly took >10% of the vote. If this repeats in the next election then there is a really strong case for PR, if we go back to the red vs blue business as usual because this was a one off protest then may as well keep FPTP.