Less data = heavier file ?

[ChameleonScales]

I just tried on the latest 2.99 dev flatpak and nothing seems to have changed in that regard.

After some more testing I'm pretty sure that a mask applied to a group will cause the xcf to contain a copy of the mask data for each layer (which can get  extremely redundant if you have many layers under a group).

I attached to this post 2 files to show why I came to this conclusion:

• the first one contains 4 layers with 4 masks, all made of pure noise. All noise patterns have a different seed, making this file contain 8 uncompressible "drawables" (as gimp calls it).
  
• the second one contains the same 4 layers but this time only one mask applied to a group that contains the 4 layers, meaning this time there are only 5 uncompressible drawables.
  

Yet, both files have a size of 1.84MB. And to be clear you can make these noise patterns large enough to make a 32MB xcf, the size difference between the first and second version will be in the kilobytes, meaning it's only a matter of which noise pattern is slightly more compressible than which other.

This would also explain why in my first experiments I sometimes ended up with heavier "group" versions.
In a group version I could be using one "not so compressible" mask for the group whereas in the "non-grouped" version, even though I was using non-identical masks (meaning they collectively contain more data than a single one), they were individually more compressible. And since the group version duplicates the data, it makes a heavier xcf regardless.

Whether my conclusion is correct or not...
Is this a known issue and is there a plan to address this memory inefficiency?
This has been a deal-breaker for me. In fact I've avoided using groups in my work since my first post on this thread (more than a year).