Seems it doesn't from test:

FILE.FileName: nostr.build_849f6e27f30faa74e3970c528fc308f3da89b2b3bfb1242d95aeb08df3b37ddc.jpg FILE.FileDateTime: 1682544580 FILE.FileSize: 67113 FILE.FileType: 2 FILE.MimeType: image/jpeg FILE.SectionsFound: COMPUTED.html: width="720" height="538" COMPUTED.Height: 538 COMPUTED.Width: 720 COMPUTED.IsColor: 0

Only the profile pics to 400x400.

All other images it compresses, converts png to jpg, but does not re-size.

At nostrcheckme we resize the images, so it is logical that they do too, I think.