Move backwards too early when the car is still rolling slightly forward

Hi guys, yesterday I drove with a good buddy (starter). It also worked out so far, if you consider that he has hardly any experience. However, he wanted to take the reverse gear towards the end of the ride while parking and did this already too early. He said he had the car roll out after the forward drive or braked, kicked the clutch and just inserted the reverse gear a little too early. So the car was still slightly rolling. I guess it w 5km/h maximum. Well, at least the gearbox got in touch easily. So there was a light noise, so it was really quiet. But everything still works perfectly. Now he thinks a lot of things. Since I’m not an expert, I thought maybe one of you experts can calm him down a bit. LG Nico