Yes, he CAN. That doesn't mean he would.
Realistically speaking, Krillin would try to fly without being able to, and would be shocked at his inability to, and would then also be shocked at bones coming out of the floor, and he would most likely just kind of try to tank the bones, suffer excruciating agony, and likely die, or if he's lucky he might barely escape, and then who knows what might happens with the rest of Sans' first attack, Krillin isn't going to have the breathing room to muster an AoE Ki blast until that attack is over. He COULD dodge in time, but Krillin's first instinct being to simply jump over regular looking bones coming out of the floor after he was forced by the weight of his soul down onto it, is not very realistic if you ask me.
Which is why Sans or incon is most reasonable. Even if we're being nice to Krillin, in no reasonable argument is Krillin getting a guaranteed win here, he has wincons, but they are not concrete, period.