well as in topic i think 2FA option via sms may be not much safe in some cases but its better because example if something go wrong with app, android/iphone got broke, simple lose phone, or let it dive into water its done (it happen all time),and what then never can got back account (or well at last its hard) via sms is simple go to provider store give id and ask for got sim card back, its simple and easy, also not all use smart phones, smart anyhing so why not...
about notification via sms well someone say not need but i think nice option when i last time login to email releated to my avi next to never (do u?) , also it allow faster reaction if something bad happen (god please not but..)
so this is my to ideas hopefully u may like it...
as always sorry for my bad english..
hugs,
Quack.