Virtual Texture compression not working

I have some Virtual Textures in my project since UE 4.25.
In 4.25 textures that use VT were always much lower size on disk (pak) after packaging.
Once I’ve switched over to UE 5.0 I noticed that this is no longer the case.

Comparison of a 4k normal texture in my project:

UE 4.25: 12850 KB
UE 5.0.1: 24766 KB

The size doubled for some reason.

Some notes:

  • I did not use Zlib/Crunch compression in 4.25.
  • Texture did not change.
  • “Lossy Compression Amount” is set to Default.
  • Oodle Texture plugin is enabled in 5.0.
  • I tried both “None” and "latest for “Oodle Texture Sdk Version”
  • Changing RDO or Lambda settings in Engine → Texture Encoding does not change anything.

Edit:
I’ve tried it in UE 4.27, the size is 13109 KB there. Just slightly more than in 4.25.