Import ISO language-region codes not supported by SDL MultiTerm (like HR-HR)

Hi,
I'm dealing with an import issue related to language-region code HR-HR (Croatian - Croatia) vs. SH-HR (Serbo-Croatian of former Yugoslavia, supported by MultiTerm, but deprecated by ISO). The source resource handles HR-HR and I could transform this easily to be instantiated as SH-HR in MTF to avoid problems during import. However, I wondered what kind of problems I might encounter, so I set up some test scenarios:

1. The MTF instance contains all sublanguages defined in the target termbase.
2. The MTF instance contains all sublanguages defined in the the target termbase except Croatian (Croatia).
3. The MTF instance contains all sublanguages defined in the target termbase except German (Germany) for example (could be any other sublanguage), but including Croatian (Croatia).

In scenarios 1 and 2 all works fine (using both subscenarios, means with and without using the sublanguage option). However, in scenario 3 import is cancelled for both subscenarios (with and without using the sublanguage option) stating that entries do not match the target termbase definition due to source:

<language type="Croatian (Croatia)" lang="HR-HR"></language>

I have seen some threads on behalf of this issue stating that the SH-HR (and may be others related to outdated codes?) will be fixed with the next update. But other threads (from SDL support) point out that if not using the sublanguage option, SDL MultiTerm would (always) import HR-HR without problem (which seems not to be true, unless I failed with my setups). Any help? I work with SDL MultiTerm 2015 SR2 12.2.1657.4.

Best wishes
Detlef

PD: If you need sample files, please let me know.