River is a club, we pick up a missed club draw; checking and giving up is the standard line.
Kh7d4c is a dry, king-high board that connects better with BB’s defend range than with our SB open range. Solver leans toward checking overall, and A6o without a club is a pure air hand that fits well into that checking strategy. If we do bet, a small 30% pot stab is preferred; the 1.3BB sizing is on the small side but still acceptable.
Turn 2c is a brick that doesn’t change the board’s overall texture. After flop bet and call, BB’s range is fairly strong and our range is still air-heavy. Solver wants us to check almost always with A6o here, and the 2.1BB bet is a small but unnecessary stab into a range that’s already showing strength.
River 9c brings the third club and completes missed club draws. We now hold A-high with a missed club draw, which is a very weak bluff candidate. Solver prefers to check and give up with this combo; betting would be a bluff with a hand that blocks some of our strongest value (Ax) and doesn’t block many natural bluffs.