I wouldn't assume that. Game companies are notorious for pinching pennies. In fact, I wouldn't be surprised if these systems were outsourced completely.
It's not a bug that a filter caught names that the merged companies now collectively do not allow in their collectively owned games.
-
The only miss here is more of a UX issue: they handled username bans the same way they handled all bans, with a shadowban.
Shadowbans are great for most infractions since you burn some time of the offender before they start again and give them little information to find loopholes with... but for something rectifiable there should be a way to nudge and explain why they're banned.
You’re right, this was a support failure, but it was also a failure of the team(s) that performed the merge.
2. Why do you think that B/A haven't spent a lot of time thinking of scenarios like this?