Here, Instapaper is likely not misusing user data, but has to catch up on compliance documentation and small details (e.g. signing data processing agreements with services they use, raising the age limit from 13 to 16, …)
But compliance isn't binary. I'm sure the data protection authorities understand the difference between “LOL I'm already noncompliant so I'll just continue business as usual” versus “Working hard to fix this – in the meanwhile, let's prevent covered Subjects from sending us more data until we are prepared to handle it compliantly.”
You can tip off the regulators if you believe that there is a violation and they will then investigate it.
Instapaper is giving a pretty good reason to be suspicious.