Yes, but assuming your phone is compromised, it can intercept the password and security key as you sign in, and take over your Twitter account. In fact if you u

Yes, but assuming your phone is compromised, it can intercept the password and security key as you sign in, and take over your Twitter account. In fact if you use your security key to sign in to anything on your phone, the phone malware can use it to access any account linked to the security key (assuming the malware has your password). So even if you don't sign in to Twitter on your phone you're still vulnerable. And even if you are already signed in to everything and think you won't ever need to sign in on your phone again, the malware can force a logout of something, and you won't be able to know if it was just some software update or expiration that signed you out. So you'll sign in again, and the malware will intercept your security key.