Merging from a descendant of an existing merge-set member

Suppose version /v2 is a descendant of version /v1, and that version-controlled resource /vcr's DAV:merge-set property value is <href>/v1</href>. Now the server receives a request

MERGE /vcr 
<source><href>/v2</href></source>

Is the server allowed to set /vcr's DAV:merge-set property value to <href>/v2</href> instead of <href>/v1</href><href>/v2</href> because it understands that /v2 is a descendant of /v1?

Roy