These can exclude a lot of common systems and software, including automations. If your heuristic is quite naive like "is using Linux" or "is using Firefox" or "has an IP not in the US" you run into huge issues. These sound stupid, because they are, but they're actually pretty common across a lot of software.
Similar thing with 2FA. Sms isn't very secure, email primes you to phishing, TOTP is good... but it needs to be open standard otherwise we're just doing the "exclude users" thing again. TOTP is still phishable, though. Only hardware attestation isn't, but that's a huge red flag and I don't think NPM could do that.