It is less secure than 2 factor auth (since it is 1 factor) but they picked the more secure 1 factor than what is popular right now.

Hopefully they are smart enough to format the txt such that the password doesn't show up in the preview, and if so, in practice, there is almost no downside to this for the vast majority if people (since if the person who now has your phone can log into the phone, the odds are they can already access your email).