A higher gain GPS antenna does little. What provides the most benefit is distancing the GPS/compass module as far as reasonably possible from electrical noise sources (ESC’s, motors, power supply wires, anything that might “cross talk”) and system generated heat. By themselves, batteries are great noise filters but they generate heat as they are used and your GPS sits right on top of one.
There are only two reasons to stuff the GPS antenna inside the aircraft body; cosmetics and cost. Eliminating the mast reduces cost in materials and assembly labor. Placing it inside makes a bird more desirable cosmetically as they look sleeker. Consumer drone buyers don’t like seeing things sticking outside of the aircraft body. That dislike costs them a lot in system performance. That includes video transmitter antennas.
In performing those two actions manufacturers sell more units, units that will never work as well as they could have.