FSLogix not compacting VHDX

Hi

Wondering if someone can tell me what I am doing wrong/not understanding?

My understanding is that a VHDX is compacted if:

The VHDX is over 1GB

There is 20% whitespace free
You are using type 0, nothing else

Right?

So what am I missing, why does FSLogix think that compaction should not be run on this VHDX?

Log says:

Disk size results: WasCompacted: false, MaxSupportedSize: 31456214528, MinSupportedSize: 591281664, SizeOnDisk (Before: 1212153856 - After: 1212153856), Space Saved: 0, Compaction took: 235
Disk was not compacted, Reason: Not enough recoverable space for compaction.

Looking at the content of the VHDX, there is around 495MB of data in the container.
The log above shows min size is 591MB, so almost 100MB more than the actual data, but ok...

The current size is 1212MB, which is over 1024MB/1GB. Tick!
So we should be able to free up 621MB, which is more than 20%, its 50%. Tick!

So why no compaction?

I have manually compacted the VHDX and it is now 612MB... I need to understand why it thinks it shouldn't compact the VHDX because I have a few other containers that are similar.

Thanks!