I also think he probably said it, but he has now gone on record and so have officials from No 10 saying that he did not. LBC are reporting that three people actually heard him saying those words, if (and its a big if) they are prepared to come forward and make their claims in public. Then BJ may be in more trouble for denying he said the words than actually saying them in the first place.I think he probably did say it, that would be typical of overstatement to emphasize a point, but it's meaningless.
I think if Covid had not happened then BJ would have got himself into trouble a lot sooner, he plays fast and lose with rules and regulations and does not engage brain before he opens his mouth a lot of the time.
I think it is too early to say if everything that is going on at the moment will affect him and the Tory part over the long term, D Cummings is said to have a lot of audio recordings. If he had a recording of BJ saying those comments about the thousands of dead piling up then I suspect Boris would be a goner. The fact that BJ and No 10 have denied the comments suggest there is no audio recording of it all.