Using smart matchers to match os,os_major

Problem:
I’d like to use a pair of smart matchers, i.e. I’d like to do:

os,os_major=Debian,10

Expected outcome:
It matches Debian 10 systems.

Foreman and Proxy versions:
2.5.4

Distribution and version:
CentOS 7

Other relevant data:
Searching in the host list with the expression:

os = Debian and os_major = 10

works as expected. But using the smart matcher shown above does not yield the correct value for Debian 10 machines.

Am I doing something wrong?