You can harp on about this forever but the fact is, indundation would provide evidence of a Flood whether the ice sheet brake apart and floated up, or remained anchored and was overlain with salty dirty water. And it would show evidence even if that layer was "washed away", because liquid water washing that layer away would leave its own disruption in the ice cores.
In other words, you can bafflegab around whatever details you like, but there is no trace of any disruption in the ice cores 4500 years ago out of the ordinary and that is not possible after such a complete inundation.
Bafflegab..... I like that. Good description.