Although this observation favours the idea that SARS2 may have recombined with merbecoviruses, it doesn’t exclude the possibility that it could have resulted from convergent evolution, whose probability of occurrence, according to the authors, is 5% (see below).
Of particular interest, we detected an array of 11 clustered homoplasies with similar genome distributions in SARS-CoV-2 and two genomes of bat Merbecoviruses isolated from Wuhan China (MG021452 and MG021451). However, simulations revealed that this pattern has ~5% probability of resulting from convergent mutations given the extent of saturation in the dataset
So I stand to my claim you think is ridiculous, ie., evidence for recombination between sars-cov-2 and merbecoviruses is not as compelling as you seem to think for it leaves room for another less likely but still plausible possibility.