We don't have the whole story of their infrastructure and that a lot of Plaid's data sources are scraped and/or aggregated and repackaged in nonstandard ways. ACH and transaction tracking have been working fine for the last 20 years prior to a clever ML system.

Nacha ACH spec per BoA for example:

https://files.nc.gov/ncosc/documents/eCommerce/bank_of_ameri...