A split submarine fleet is not going to happen, multiple officials including the Prime Minister have confirmed this. So much of the value in these bids is tied up in their associated content, that same content is going to largely disappear if one company doesn’t win the bid. TKMS has already stated recently that their bid would basically lose all of its appeal if a split fleet was chosen.
The fighter review isn’t remotely comparable to the submarine procurement, the sheer amount of industrial offsets and bonuses are on a different level. That’s not even getting into the logistical burdens this will place on the Navy for effectively no reason. Any kind of split doesn’t make sense and I would be entirely blindsided if this option is exercised.