Debian 10 Kolab 16 upgrade

Hi list. 

Debian 10 with Kolab 16 here, sources:
deb http://obs.kolabsys.com/repositories/Kolab:/16/Debian_10.0/ ./

(yes, probably time to give Kolab on Debian 11 a second try ;-) )

I'm using the following preferences file for years now:

## /etc/apt/preferences.d/kolab
Package: *
Pin: origin obs.kolabsys.com
Pin-Priority: 501
##

Since some time, I don't know when, dist-upgrade always says to "downgrade" php-net-idna2 as there are packages of the same version in Debian and Kolab. The following entry fixes my problem:

##
Package: php-net-idna2
Pin: origin obs.kolabsys.com
Pin-Priority: 99
##

As this package is AFAIK not needed by kolab, this problem probably hits only a view people. Still the question is: why is php-net-idna2 in the Kolab repos without need? Is there some need?

regards
hede