Not strictly true.
As recently as last month, the Minister said that the R1 and MRA4 remained possible options (with Helix, and thus part of an L3 bid), along with the favoured Rivet Joint.
He did make it clear that BAE's latest proposal (a proposal, not a commercial bid) did not meet his required ISD, but he did not slam the door on a revised proposal from BAE.
However, though Parliament has not been told, all the indications are that the decision has already been made, and that the Minister was playing silly b*ggers.