I could and most likely be wrong here but I thought that PSD2 only applied to electronic payments and doesn't necessarily apply to just logging into your account to check a balance,
I would assume that logging into the online portal isn't restricted to "view only" and therefore they have applied the security level for payments to account access as well
why as JPD says can I log into my account with only my phone but with my computer I have to have a second electronic device like a phone
Surely if it's "mandatory" it applies to all ways of accessing your bank account??
This is, I believe, due to use of app rather than website. If you're using the app, there is already verification of the device. Unlike SMS or email, messaging and interaction with an app is pretty secure. If you're logging in through a website, you're device isn't verified and so you get the second factor.
One way to check this - try logging on to the website on your phone browser (as opposed to the app). I'd assume you will get the verification request as you do on a PC