ca-valencia treated as ca / ca gets suggestions from ca-valencia, ca-valencia gets none

[cloph]

E.g. query amagama for suggestions for one of LibreOffice Help strings

<variable id="landen">Choose <switchinline select="sys"><caseinline select="MAC"><emph>%PRODUCTNAME - Preferences</emph></caseinline><defaultinline><emph>Tools - Options</emph></defaultinline></switchinline><emph> - Load/Save</emph></variable>

when selecting target language ca, you get both ca and ca-valencia results (desa vs guara for "save")
However when selecting ca_valencia, no results are returned.

See also https://translations.documentfoundation.org/ca/libo_help/translate/shared/00.po#unit=108657847 (the ca-instance of the string and
https://translations.documentfoundation.org/ca-valencia/libo_help/translate/shared/00.po#unit=108650803 for the same string in ca-valencia - it doesn't get any suggestions.

There's similar issue #3202, (although tr an az are different locales, so likely completely different reason) and #2556 that probably describes the reason...