can I trust the gain plugin's "find level" result?

[Lowendr]

hi out there!
Our problem is that we will check levels on a track or tracks using the gain plugin under Audiosuite, by selecting across what seems to be the highest amplitude area on the tracks, then clicking "FIND LEVEL" --we then get a peak and rms reading. We made no further adjustments.

With no plugins active, and no volume automation changes -everything at default unity gain, we then Bounced the same selected areas, then reimported that bounced region into a session.

Then we checked our bounce with the gain plugin again, expecting to find the same rms and peak.

THEY'RE NOT THE SAME. We are getting discrepancies of anywhere from 1 to 4dB difference between pre-bounce and bounce when measuring with the gain plugin.

What gives? Can we not trust the gain plugin?