I agree. But would add that with a head gasket leak it often goes both ways, getting some exhaust gases dissolved in the coolant. Any competent garage can also do a simple test for exhaust gases in the coolant, which would also indicate a head gasket problem. I believe nowadays they even have some simple test strips to test coolant for exhaust gases, sorta like litmus paper or the strips you use to test for ph.

I would think any competent technician when faced with a chronic loss of coolant and good pressure test results would test the coolant.