They are frequently not even given any information about what kind of target they’re attempting to observe, and in dedicated groups (particularly those the govt had running for decades) train/practice every single in groups to hone their skills.
Having said that, the remote viewing community does not take UFO-viewing claims seriously. There’s one fellow in particular who is constantly overriding people’s boundaries and giving them aliens-based targets against their wishes (and against their knowledge, as I said before).
Viewing targets for which you cannot later confirm the quality of your signals is considered the most inaccurate and unreliable way to go about things. Obv we can’t verify things we can’t go out and physically observe.