FWIW, I've just returned from a trip that took me along the stretch in question. This morning when I went through there northbound at between 08:00 and 08:30, there were two guys in L4 just before the hatches exchanging details
Even though there is adequate signage, the closure of L4 seems very abrupt and I suspect that they could usefully extend the "snape" of the hatches.
The other thing that I noticed was that traffic was moving a lot slower now that there are four lanes than when there were three. The merge between L3 and L4 starts almost as soon as the fourth lane appears because those who know seem not to want to be hung out to dry in L4 with nowhere to go. FWIW, this morning it was stop-start in L3 and L4 with the crawler lane moving faster than anything else.
On the whole, this has to be one of the poorest examples of traffic engineering on our motorways.