When you start a specific claim, are VBA looking for other things in your VA records to deny or lower rating not related to that claim?

More of a question for VA benefit workers I guess but let's say, for example- I file a claim for migraines and have medical records of my migraines being worse. And let's say I'm also connected for gastritis already.

In my records, say the doctor puts "veterans gastritis has been under control, better, so on and so forth".

If I didn't pit a claim in for gastritis, will they look at that and try to lower the rating based on docs notes or trigger a C&P, or are they strictly just looking for the migraines records? Curious how that works. Thanks.