there will be people who will still hack, ... there is another hoop/hurdle they have to pass to do

Unless they have a working phone number. If this is their idea of increased security instead of server side detection, people have already had years of practice and experience with what works and what doesn't.

I am sure they are working on it as well to make it so everyones numbers can work,

The fact that it blacklists certain providers would've been MORE work to implement. If you write code that says

send code to #number, open text field, if code is entered, compare to code sent to #number, if equal then pass. That's fine, but they wrote like

send code to #number, open text field, if code is entered, compare to code sent to #number, if equal then verify phone number against a list of providers we don't feel work with the type of clientele we want in our game. If their number is not on this blacklist, then pass.

This is 1, fucked up, 2, fucked up, and 3, already extra work than a straight 2 factor authentication. They don't need time to research and development a check they specifically put in.

They have the choice of effecting a smaller amount of the community or ruining the fun for everyone from hacking. Not an easy or perfect choice, because if they didnt do anything people would complain about how Blizzard hasnt tried to do anything about hacking. No matter the choice they make to the public they did something wrong or are shitty.

It wasn't a flip of a switch. There's no on or off state for this shitty behavior. Theres a huge amount of area between allow all hackers and fuck over consumers. How about server side cheat detection? How about a not completely worthless report function?