That's not quite true.
See the entire idea behind defining a common mechanism
for signalling policy in communities in a flexible way for
both intra and inter-domain use is to help you to use the
same encoding acros policy engines of many vendors.
I would actually risk to say that it could be even more
applicable intra-domain then inter-domain.
See the crux of the thing is that this is not just about
putting bunch of type-codes into IANA reg. It is much more
about uniform encoding for your actions with optional
parameters across vendors.
In fact the uphill on the implementation side is not
because signalling new value in BGP is difficult to encode
... it is much more about taking those values and
translating those to the run time policies in a
flexible way.