Yes of course, that's why they are proto-personas. As a matter of fact, if you have some user data, protopersonas will be way more accurate.
A proto-persona has four quadrants:
- Biography & Picture
- Needs & Goals
Proto-personas are completely subjective and based on your team's idea of who your users would be.
It's easy to see that if you have some surveys or Google Analytics, you can add some pizazz to these proto-personas and infer REAL demographics, REAL behaviors and even REAL needs and goals. Of course, this will depend on the analytics you have, but having some data will always be more accurate than having no data at all.
However, the concept of proto-personas creation requires that not only you creates them, but you'll need different views from different people in your team. And I understand that your stakeholder's time might be valuable, but time restrictions is not an excuse. It may take like 10 minutes to create a proto-persona and these 10 minutes will be highly compensated by the obtained results