The only place I have had problems with that technique is coming up from Chester to Barbridge, every lock seems to behave differently.
At least Anderson Boats go to a lot of trouble trying to train their hirers before letting them lose, the best I have ever witnessed
If I am passing through a Thames lock unattended then I run a longish stern line to a bollard and take the bow line ashore to control the boat while Diana operates the lock.
That is why at least one of us is always ashore in the lock. I have had Volockies say get back on the boat, but I just say I'm fine ta. The worst one was going down Bunbury Stair Case locks, with another boat wo said "O good, a volunteer I don't need to do anything" The said volunteer then opened the paddles walked over to his chair in the sun facing away from the lock and read his news paper. Diana was ashore on my side