No, you have it wrong.

The four gates at SXM, that have jet bridges, are gates A1, A2, A3 and A4.

Planes that arrive at gate A4 are deplaning by stairs or ramp and walk to the TAF (temporary arrival facility). Planes that arrive at gates A1, A2 and A3 are deplaning by stairs or ramp and are bussed to the TAF. All planes departing from gates A1, A2, A3 and A4 are using the jet bridges for boarding. That is the current situation.
Carry on.