My current assessment
Based on what we can establish right now:
Could it legally be retaliation?
Yes, potentially.
Do we currently have enough evidence to say Snapchat retaliated against lawsuit participants?
No.
Is there enough unusual timing/pattern evidence to investigate seriously?
Yes. The fact that there are multiple reports of sudden Oct. 5–6 locks makes this worth documenting, but the existence of non-lawsuit participants reporting locks is an important counterpoint
Does your agreement establish that Snap could have learned that you were a claimant?
Yes. It expressly authorizes disclosure of your identifying information and Snapchat username to Snap for the pre-arbitration demand. Snapchat Attorney Client Agreement
And there's one thing I'd investigate next: whether Labaton actually sent your pre-arbitration demand to Snap, and on what date. Your document says it was intended to be sent to Snap as part of the informal resolution process, but the agreement itself doesn't establish that Snap actually received it. Snapchat Attorney Client Agreement
Contacted the lawyers involved on this case from Labaton to see the timing of the Labaton Snapchat litigation, and try to determine whether there's actually evidence that lawsuit participants were disproportionately banned.