If the NAIPs App isn't approved by them, then yes Car RAMROD, it isn't legal for most purposes.
As I believe I've mentioned before, it isn't just the simple act of gathering weather, there are checks and balances that need to occur during that process for an approved source.
If it's not an associated App then anything that ASA or BOM change on their end they won't be alerted to necessarily, it means it's integrity is not at the same standard.
I'm not saying it's a massive risk, 99% of the time it'll probably work just fine, but you need to keep in mind there is a risk using unassociated Apps.