I am a relative novice here who has tried to do more IDs as a way to increase exposure to species and to learn more - and yes, lockdown has been a factor in giving me some time. I commented on this issue in a discussion that flowed from the stats put up a couple of weeks ago regarding the site reaching a milestone number of observations.
I agree that new users might do as you describe - though we don’t know what sources were reviewed in the gap between the IDs. But sometimes, the scenario may be playing out as you suggest.
There may an upsurge in this because of the pandemic, new users, esp using the app?
To follow your suggestion above re users X and Y: broadly seems a good idea, but level of ID would need to be considered so with no ID at all, what you suggest sounds fair, and probably with allocation to eg flowering plants as well.
Another possibility is to have a pop-up at the point where that user (ie the one who posted the observation with either no ID, or with a high level ID only such as flowering plants) hits ‘Agree’, to say something like: “Please don’t just agree because someone else has proposed this ID. Can you positively identify this observation to this level for yourself? Yes? Then go ahead, agree!”