In the Tyne and Wear archives they have it listed as Mathew Turnbull (sic), but they also have a Sowerby trinket set attributed to Mathew Turnbull too.

So, I'm assuming that is where the attribution for it being Sunderland Glass comes from, without them claiming Turnbull as the manufacturer. They are both of part of the collective Tyne and Wear Archives and Museums.
I do point out the occasional oddity to them

, and have asked them if they can clarify the source of their attributions in the past, but last time they said they were working restricted hours and had restricted access due to Covid.
It's possible I could start harassing them again

, but not sure if it might put them off from liaising with me on my vocational project next year (she says hopefully).