David Wright In the supported operating systems section ArcGIS Pro 2.1 system requirements—ArcGIS Pro | ArcGIS Desktop we show the latest update or service pack tested. Here is an example from ArcGIS Pro 2.1.
(For Pro 2.2, the latest update tested is Version 1803 with May 8, 2018 update)
Note that the page also says, "Prior and future updates or service packs on these operating systems are supported unless otherwise stated. The operating system version and updates must also be supported by the operating system provider."
There is also the Supported Environment Policy. It seems that these should address your concern.
Does that help?