I know we've spoken about this a few times already but sadly I still haven't come up with a definitive answer as to why it is happening yet but I do have a semi-tested theory......
As we know 2K21 seems to process the lidar data differently than 2019 did so the amount of object meter just the lidar terrain uses up can be a bit "weird" sometimes when you first open the course in the 2K21 designer. To begin with it can show the object meter at 100%, but then as soon as you do any kind of edit at all it then drops to a much lower figure like 50 - 60% or even less.
I haven't tested it thoroughly enough so far but I'm pretty sure the lidar trees not being carried across from 2019 is something to do with the above "glitch" combined with how the overall course "file size" is now determined by 2 separate meters - objects and memory.
I'm guessing that if the size of the lidar terrain plot you create (or maybe just how much you leave unmasked) is too big and therefore uses up too much of the object meter when it gets imported into 2K21, that the game decides to still generate the plot but just not add the trees because there is not enough space left in the object meter to allow it. Previously in 2019 if the same thing happened it would just not create the plot in the first place, or at least it wouldn't allow it to be opened.
It's late so I probably didn't explain what I mean very well so apologies if that's the case, but hopefully some of what I typed will make a bit of sense
*Edit
As a rough but easy test to my above theory I just quickly dragged 2 other lidar courses into 2K21 that I hadn't previously. They are both relatively small in terms of the unmasked lidar area size and both have full lidar generated trees. When they were both first opened in 2K21 all the lidar trees were generated ok and the object meter was only at 50 - 60% without having to do any edit to drop it from 100% as I described above.
