There are numerous factors involved as far as a given named storm maintaining hurricane strength well inland but it certainly does occur. Houston is fortunate that this stalled storm didn’t draw energy to sustain windspeed in addition to moisture from the gulf.
Actually the reverse is true, if Harvey had the energy to sustain wind speeds, it would have turned North and left the area after about 24 - 30 inches or rain instead of over 50 inches. Lacking the energy, it stalled out up against a high pressure system. The it was feeding of itself, not the Gulf.