Unless the system you use the check that balance is compromised on your end or their end. If you have malware, they can be looking at the same numbers you’re looking at, so that isn’t fool-proof. If your account is already compromised, they may just be phishing for 2fa tokens to initiate some kind of account change, like the kind that would complete their total account takeover, at least until you or the bank notices suspicious activity.

i mean if you have malware, all bets are off IMO. But good point.