I did this in February of this year. It is called a side to side as KYBOB stated. Here is my experience, and know that Princess was well aware of our upcoming plans.
We were given a Covid test the afternoon or morning prior to disembarking the Regal Princess. If we didn't pass they would come and get us. They didn't, so we knew we had passed. That evening we had instructions about the process the next day and were given a printed confirmation of the test results that evening. . We were to disembark late in the disembark process and tell the person arranging the transportation that we were going to board the Sky Princess and needed to be bussed over. They put us on the next bus - which was also the last bus and took us over to the garage for Berth 4 and we almost got left there but I made sure to tell the man that we were suppose to go to the bag drop off for berth 2. I know he had been told by the dispatcher but obviously forgot. He did take us over and we dropped our bags and then got in line to board the Sky. Regal was at birth 19 and Sky was at berth 2.
The most likely scenario for you on side-to-side day will be Enchanted at berth 2 and Sky somewhere else like 19 or 29 so you will need to either take the bus or grab a cab. Ask at guest services if the bus will take you. They may not. I honestly think if I had to do it over again, I would opt for a cab.
I hope this helps.
