Wait what? Did they really ask for your bank login credentials? If so, approximately what date was that?
This is a very common thing for fintech companies to do.
Yes. All the work of "don't enter your bank password on any website that isn't your bank" went down the bloody trash once this awful workaround to the awfulness that is ACH happened. It's very sad.
Not sure if this is what they use now, but Mint used a similar (but older) service to Plaid called Yodlee [0] as their backend for accessing bank accounts.
[1] https://techcrunch.com/2009/09/18/mint-is-yodlees-youtube/