Not unusual, and there are likely a number of contributing factors.

Falcon launches to the ISS typically have an instantaneous launch window (roughly, when the plane of the ISS's orbit sweeps over the launch site). If they miss it, they try again about a day later.

Falcon (both Heavy and its little sibling Falcon 9) uses subcooled densified propellants which limit how long it can sit waiting for launch while fueled before the LOX warms and expands too much.

A short window means they only have to compute and verify and program one trajectory.