Fails to process PAK structure with versioned _P packs

[Kein]

Posting this as a full-fledged issue incase you might want to look into it later.
Tested on Talos 2 demo, 5.2.0 it has IOStore/PAK structure:

Talos2-Windows.pak
Talos2-Windows_0_P.pak
global.ucas
global.utoc
[...]

LogIoStoreTools: Display: Successfully opened 3 Container files
LogIoStoreTools: Display: Building Package Map from Containers
LogWindows: Error: appError called: Assertion failed: PackageBuffer.IsOk() [File:D:\Perforce\FactoryGame_dev\UE4\Engine\Source\Programs\ZenTools\Private\IoStorePackageMap.cpp] [Line: 74]
Failed to find ChunkId 7eca92f3c72d030000000001 for PackageId 0x32dc7f392ca7e in ContainerId 0xdb448bc18f368bcf (ChunkInfo valid: 0)
LogWindows: Error: === Critical error: ===
LogWindows: Error:
LogWindows: Error: Assertion failed: PackageBuffer.IsOk() [File:D:\Perforce\FactoryGame_dev\UE4\Engine\Source\Programs\ZenTools\Private\IoStorePackageMap.cpp] [Line: 74]
LogWindows: Error: Failed to find ChunkId 7eca92f3c72d030000000001 for PackageId 0x32dc7f392ca7e in ContainerId 0xdb448bc18f368bcf (ChunkInfo valid: 0)
LogWindows: Error: [Callstack] 0x00007ff7a3871393 ZenTools.exe!FIoStorePackageMap::PopulateFromContainer() [D:\Perforce\FactoryGame_dev\UE4\Engine\Source\Programs\ZenTools\Private\IoStorePackageMap.cpp:73]

I think they might be using the little-known "overwrite-delete" file entry that "deletes" assets from original PAK via _P(atch) outright, rather than overwriting?