My guess is that they have few users using Firefox plus either (a) some Firefox-specific vuln was blown way out of proportion, enough to get Legal to block this browser, or (b) their front-end devs haven't discovered Playwright yet and don't know how to run e2es against it, which MBNA considers a non-starter

Either way, horrible decision on their part, especially now that firefox usage might be ramping up due to Manifest v3 concerns