He hasn't once said he's changed his opinion about June 12th. Considering it was an allegation of harm on 12th, and not murder (on 13th), it wouldn't be reflected in the charges even if it was his opinion. He said "can't rule it out". Other things like the insulin happened when LL was off shift. It is what it is, and you are suggesting that the experts are manipulating this case to shore up a prosecution.
He said he updated his opinion based on the reports of other medics, the radiologist and pathologist, opinions he wouldn't have had at the time of his reports, which as he says, is what clinicians do when additional information becomes available.
There is zero evidence that there were conversations between Dr Evans and the prosecution regarding his opinions about 12th June, which were not material to the charges. Please quote the part of his testimony where he says he changed his opinion. There would be no point, knowing that the defence would have copies of all of his reports.
With regard to Dr Bohin she added to the part you have quoted -
She said one conclusion for Child C's collapse was CPAP accumulation of air, the other being deliberate injection of air.
She said
the doctors did not appear to have a concern as they had noted the abdomen to be "soft".
Recap: Lucy Letby trial, Tuesday, November 1
Another expert paediatrician, Dr Sandie Bohin, said she believed the only plausible explanation for Baby C's collapse was an introduction of air into his system.
Baby 'suffocated when Lucy Letby injected air into his stomach': trial