If I'm reading your linked code correctly, SpecifyModel takes in conditions (with onsets/durations) and regressors (which are vectors with numTRs entries).
This model is then passed to the session_info field of level1design, which also specifies a convolution with the dgamma basis function.
In the documentation for level1design, here,
I don't see any mention of the conditions being convolved and the regressors being left alone. Is this a problem with the documentation, or am I fundamentally misunderstanding something?