Delete on import does not seem to work

[Terrails]

VERSION INFORMATION

Server Version: 4.1.2.0 (d0316b6)

DESCRIPTION

Settings in multiple files section of desktop are as following:
Delete on Import is checked
SUBGROUP is on top of types
Subgroups contain all the groups that are being imported

1. Group lower in list gets imported (e.g. subsplease)
2. Group higher than the previous ones get imported (e.g. lostyears)
3. The first lower group file is not deleted on import

STEPS TO REPRODUCE

configuration file: https://gist.github.com/Terrails/13989d1390290c5e36b9d2ed9fe79806

[ElementalCrisis]

@da3dsoul can you confirm since you wrote this code.