Witnessed Signature Dates and Discrepancies 0

[Tnexus]

I have a question regarding signature witnessing and the dates on the slab. So I'm a fan of Radiant Black by Kyle Higgins and ordered some of the exclusive signed copies of issue #1 of the foil versions in January of this year from ComicSketchArt. These were limited to 50 copies. I noticed on Kyle Higgins' Instagram that he signed these on Feb 27th. However, one of these for sale on Ebay shows on the slab that the signature date was 05/02/2021. (I'm still waiting for my copies.) I can understand 1-2 days of discrepancy maybe, but 63 days is a huge red flag to me. The signature looks the same to me on the slab and the photo, but obviously this was never witnessed if the dates are that far apart. Below are the two links in question.

https://www.instagram.com/p/CLznEpUh59A/

https://www.ebay.com/itm/154594885356

I don't do Signature Series books that open, so is this normal?

[Beyonder123]

This leads me to believe that these books weren't witnessed at all. Perhaps the date on the slab is the date that a CGC rep picked them up?