Not really, as they couldn't get data from an MSC product that...

Not really, as they couldn't get data from an MSC product that has been approved based on data in adults to compare it against: "the Janus kinase inhibitor ruxolitinib has been approved for the treatment of SR-aGvHD by multiple regulatory authorities, including the US Food and Drug Administration."
https://www.nature.com/articles/s41591-024-02990-z

They could have used the data from Japan, which reported "At 52 weeks, 12 patients (48 %) treated with MSCs only (six patients) and MSCs plus additional treatments (six patients) were alive in CR", but I couldn't see a follow-up for 18 months (I must admit I spend as much time looking for it as you did researching your post).
https://link.springer.com/article/10.1007/s12185-015-1915-9

Interesting is the reference to MSC-FFM, which is an approach taken in Germany that @JB1975 first mentioned years ago, and the results I have shared on here a few months ago, "Furthermore, a recent study of ‘real-world’ experience with a bone marrow-derived MSC product reported that the probability of overall survival in adults with ruxolitinib-refractory aGvHD after MSC treatment at 6, 12 and 24 months was 47% (38–56%), 35% (27–44%) and 30% (22–39%), respectively."
https://pubmed.ncbi.nlm.nih.gov/37990219/
Their approach is very interesting, since there starting material is not made from one donor (per Master Cell Bank), but instead "manufactured from pooled BM mononuclear cells from eight HLA-disparate healthy donors. MSCs are selected by plastic adherence, expanded in platelet lysate–enriched media in 2D culture to the end of passage 3, then frozen in saline-albumin with DMSO at a final concentration of 10% v/v until immediately prior to infusion."
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10664468/
This method may "average out" some of the hurdles brought up by the FDA and discussed by @JB1975 using graphs presented during the ODAC meeting:
"However, there is a high level of interdonor variability in the propensity of MSCs to be activated by IFNγ and TNF, and thus in their capacity to express indoleamine 2,3-dioxygenase5,6,7. MSC gene expression, differentiation, proliferation and colony-forming capacity are also donor-dependent and tissue source-dependent2,8."
https://www.nature.com/articles/s41591-024-02990-z
However, too early to say.

Shame that a positive article always ends up being used to try and cast doubt. Now and then, I am happy to "play ball", although being in a more moderate way now as usual.