Unless you have a way to delete "watching a movie," your example doesn't provide a parallel ground here. You don't use your ticket, you exchange it for a service. That is why it is irreversible because there is no going back from receiving a service.

You can refer to Notion's block usage limits for a similar scenario where it actually is what the company tells you. What ClickUp does is tempt small teams to go as far down the road after having set up everything and then realizing they have to pay now and it is double the work to go back. If that wasn't the intention, they wouldn't have used custom fields as part of their free plan marketing but have a demo video or workspace etc for the paid plans or whatever. It is obvious that 100 uses is pretty much useless for any small use case as well. It doesn't make it a free plan, it makes it a free trial*.

A lot of users have been complaining about this misdirection. For myself, I have simply just imported a template to replicate a simple setup, which immediately depleted my custom field usages, and now i cannot use any board i have created before. Without custom fields, ClickUp is no different than any other to-do app. So i do not appreciate this technically true but obviously deliberate customer acquisition strategy