Never mind. The floor layer did lift them according to my request to make alterations. Those planks must be the pure click type. When I was looking at them, I felt some stickiness around the click-able areas. So, I was concerned they applied glue to the click, making the planks not lift-able.
The under lay is 20 year old square vinyl tiles glued on concrete.
Is there such thing as a wet click? That was what I was concerned about originally. The thin vinyl planks come with their own (probably rubber) underlay. They are this: https://www.toppstiles.co.uk/rigid-core-luxury-vinyl-tiles/owsten-grey-herringbone-luxury-vinyl-tile
When you glue laminate planks, some of the glue goes into the HDF boarding, the rest squeezes out the joint, with Click LVT it will either clog the joint or all squeeze out. The glue sticks the joint together but doesn't make it more self supporting so over a hollow etc the much thinner tongue of the LVT is far more susceptible to creaking and cracking/splitting.Before the reflooring, I had laminate that I did myself. It was tongue and groove that I glued. This was where I got the "wet click" idea from. I had no problems with the laminate as a first-time DIY layer. The vinyl planks are less than half as thick as the old laminate. I would not be surprised if the new planks are flimsy. There were some broken old under-tiles. I doubt the floor layer cared and carried on regardless. I will be selling the flat. So, it will be the next guy's problem if the floor falls apart.