I have not heard of anyone claim that the PIC cross country hours for the instrument had to be post private.

And as you said, a reading of 61.65 does not support it. The usual language in the FAR that signals "the pre-private flying doesn't count" is "in the areas of operation..." in a particular section. When used, the phrase has been interpreted in various scenarios to mean that you can't use tasks from another certificate or rating to count.

In 61.65(d), (d)(2), which talks about instrument time in "certain areas of operation" uses the phrase. So that one is limited.

But 61.65(d)(1) which talks about the cross country requirement does not. So any cross country loggable as PIC is applicable, including solo student cross counts.

The examiner is wrong. He should reported and retrained and if he is turning away applicants with proper credentials, hopefully the system may take care of itself - as the word spreads he'll simply stopped being used.