Don't know much about the set, but a quick search on COMC shows that they only have 1 Matte White 5 stripe (MBC-21), and it absolutely IS serial numbered (out of 40 in this case):
https://www.comc.com/Cards/Football/2021/Wild_Card_MATTE_White_-_Base_-_5_Stripe/MBC-21/Greg_Rousseau/18560817
Under their "Parallels and Grades list", they have "5 Stripe" and "Retail 5 Stripe".
My guess (and It's only a guess, although I'd argue a semi-educated one) is that maybe the Retail cards are not serial numbered and we need to add checklists for them, but I don't know enough to add them for sure.
David657 wrote:
2021 Wild Card Matte White 5 stripe Paulsen Adebo MBC-47....I did delete the SN50 note for that specific ard but thought Id ask for clarity, before "correcting" CL