I can confirm that the 'Traction battery heating' option is available in my 2023 MG ZSEV SR. Yesterday, I did a 125 mile journey (each way) and had the slow charging issue. This was on an Instavolt, Gridserve, and an EVPoint on the way back. I suspect the Insta and the Gridserve may have been throttled, but the EVPoint ones are recently new, it was 9:30pm and I was the only car there. It maxed at 46kWh. I turned on the battery heating about 20 minutes beforehand.
90% of the time, I agree with the philosophy (and enjoy it) of not worrying about how long it takes. However, when it is winter and you are motorway driving, late at night, needing more than one charge on the journey meaning range is greatly reduced, with no children to accommodate, you do want your car to charge rapidly. I can't imagine what this would be like for a travelling salesman who was on the road all the time.
Like many other aspects of the charging experience, there is still some way to go in improving this! That being said, I would never go back to an ICE simply for the convenience!