GIMP includes color profile into bilevel tiff image, making the image size much bigger

GIMP version:2.10.x

Note: bug reporters are expected to have verified the bug still exists either in the last stable version of GIMP or on updated development code (master branch).

Operating System:win10

Package: [flatpak? Installer from gimp.org? If another installer, tell us where from]

Description of the bug

Please describe your issue with details. Add screenshot or other files if needed. As described in the subject.

Reproduction

Is the bug reproducible? [Always / Randomly / Happened only once ] Always.

Reproduction steps: try to modify a bilevel tiff image compressed with CCITT G4 just quite a little bit (so that one would not expect that the file size would change much), and overwrite the original file. Now the file size is more than twice as big as the original size. The next time when the modified file is opened, a message pops up with the question if the included color profile should be converted. A bilevel tiff image needs no color profile, and CCITT G4 is THE COMPRESSION METHOD which has the most large compression rate.

Expected result: The modified bilevel tiff image should not contain any color profile and the file size should not be visibly increased after a minor modification.

Due to this behavior (and another bug with the lasso tool I'll report in another bug report I've switched back to GIMP 2.8. which does not has this error.

Actual result:

Additional information

If you have a backtrace for a crash or a warning, paste it here.