Totally agree with this. I show in the 3’3 and rarely jump a full course of 3’3 at home. I didn’t before I moved up, either. There will be 1 or 2 thrown in but a course of 2’9-3’-3’3 with different tracks, rides, etc is more than enough.
I do agree you should be jumping THE height at home in some fashion so you can be prepared for the height at the show. But I think demonstrating mastery of pace, connection, track, and execution at 3’ is going to give you much better prep than just galloping around a 3’3 course at home without any of the above and saying “yep, I did it!”