Maybe we’re not talking about the same thing? I was thinking about the diapsid debate, where genetic evidence is overwhelmingly strong in favour for diapsid evolution Mitochondrial DNA evidence: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC24355/ Micro RNA evidence: https://pubmed.ncbi.nlm.nih.gov/21775315/
Tbh a core multi gene ML tree to all other reptiles would prove it beyond a shadow of a doubt, maybe someone’s done that already but I haven’t been able to find it.
Three robust genetics papers using different sequences and genes, each time place it as a sister group to Archosauria:
248 nuclear genes (187,026 nucleotide sites): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3473239/
1145 ultraconserved elements (UCEs) and their variable flanking DNA: https://royalsocietypublishing.org/doi/10.1098/rsbl.2012.0331
1,113 single-copy coding genes, robustly indicated that turtles are likely to be a sister group of crocodilians and birds: https://www.nature.com/articles/ng.2615
This level of genetic evidence is an overwhelmingly strong signal, regarding relationships and recent common ancestry to extant species. I would say it is undeniably strong. You cannot possibly get evolutionary convergence over this many genetic loci.