If I tie the breakers together, if there is a ground fault by either line it would still open the circuit at designated time/sens of the manufacturer.. As I understand it, the only thing a GFCI breaker does that a regular breaker doesn't is it measure an unbalanced load between nuetral and line, ... still the same, if a ground fault occurs it should still open the circuit at a much quicker rate (3-5 Ma/ 25ms) which still serves its purpose ?
Using two single pole GFCIs with a handle tie on a double pole load (that has no neutral) will result in the breaker(s) immediately tripping every time you turn them on when the load is drawing current.
Think about what you understand about the operation of a single pole GFCI . . . it is correct. In a single pole, the current leaving the breaker on the hot is measured against the current returning on the neutral.
Hooked up to the load as you propose, each single pole breaker will always try to trip every time the load trys to draw current, because there is no way for the return current to be on that single pole breaker's neutral.
The two single pole breakers will compete to be the first to trip, interrupting the current, and sometimes one, or the other, or both breakers will actually trip.
Bottom line, you'll never be able to turn on the load.