I have confirmed with several test trials in 1.19.10 on a Realm. I am on MCPE though, which shouldn't matter for the realm, especially since the owner created it via Win10. I have done some tests on single player and it indeed seems to be an issue with unloaded chunks. It happened even with "/spreadplayers ~ ~ 16 64 @s"(I believe the chunks were still loading) but started working correctly when i lowered the range to "/spreadplayers ~ ~ 16 32 @s". It always happens for me for longer ranges. After testing on the realm, it seems the conclusion that it is related to unloaded chunks and my conclusion that chunks merely hadn't loaded yet for the max 64 range version are true. Using "/spreadplayers ~ ~ 64 128 @s" generally works as intended on the realm while it breaks at "/spreadplayers ~ ~ 128 256 @s" and longer ranges. I do believe the realm simulation distance is 4, possibly 5. If there is any more information that could help, please ask and I'll do my best to acquire it for you.
Thank you for your time and effort,
Haleon
P.S. I was doing tests as I was writing this comment to include as much useful information as possible. That is why it is written the way it is.
HaleonGoemea
I have confirmed with several test trials in 1.19.10 on a Realm. I am on MCPE though, which shouldn't matter for the realm, especially since the owner created it via Win10. I have done some tests on single player and it indeed seems to be an issue with unloaded chunks. It happened even with "/spreadplayers ~ ~ 16 64 @s"(I believe the chunks were still loading) but started working correctly when i lowered the range to "/spreadplayers ~ ~ 16 32 @s". It always happens for me for longer ranges. After testing on the realm, it seems the conclusion that it is related to unloaded chunks and my conclusion that chunks merely hadn't loaded yet for the max 64 range version are true. Using "/spreadplayers ~ ~ 64 128 @s" generally works as intended on the realm while it breaks at "/spreadplayers ~ ~ 128 256 @s" and longer ranges. I do believe the realm simulation distance is 4, possibly 5. If there is any more information that could help, please ask and I'll do my best to acquire it for you.
Thank you for your time and effort,
Haleon
P.S.
I was doing tests as I was writing this comment to include as much useful information as possible. That is why it is written the way it is.