The only way I can see it getting jammed, using the inner and middle shift positions, is if you set the high limit screw to stop the FD; which you don’t need to do. There is no middle limit screw stop to set on a triple and it doesn’t overshift. Of course you have to set it to prevent another shift.
It can become a bit of an art form getting the right low limit, cable slack, or lack thereof, so that the shift works correctly. Actually, I set the high limit after I’ve got everything setup correctly with an STI. That way there is no pressure or forcing against a hard stop. I just try to get barely backed off.
Running a triple STI shifter with a double crank requires a high limit to stop from shifting to a non-existent 3rd chainring. A double STI shifter with a double crank makes a high limit a bit redundant; but we all set it. Same with a low limit setting on an RD with an STI shifter. And it is just as possible to force a RD shifter pawl with a bad low limit setting.
John