If a unit dose syringe contains too much activity, can some of the contents be squirted out without invoking USP <797>?

Yes.

Squirting excess volume out of a syringe can be considered administration, so USP does not apply. It should be noted, however, that this activity will expose a critical site (i.e., the syringe tip or the needle hub) to nonsterile air and thus increase the risk of contamination. Care must be taken to avoid touch contamination. In the spirit of USP <797> regarding critical site exposure to nonsterile air, the syringe contents should be administered within 1 hour of this action.