Consider Trek's sizing and geometry. Let's compare the geometry from their FX hybrids vs their Pilot road bikes. The Pilot is their least aggressive road bike, designed more for comfort.

Let's use the sizes they designate as Medium, which are roughly equivalent, which would be their 20" FX vs their 56cm Pilot.

The 20" FX has an effective top tube length of 56.8". The 56cm Pilot has an effective top tube length of 55.0".

So if one would convert an FX to a drop bar, and use the same stem length on both, then the hand position for the FX conversation would be 1.8" further out than on the Pilot road bike. That's quite a difference. Much more stretched out.

A hybrid frame is designed for having the hand positions to be much closer to the head tube, so they use a longer top tube to account for it. Thus if you swap out the flat bar for a drop bar, it is going to move the hoods further out than they will be on a road bike frame. So you need to shorten the stem to adjust for that.