While you cannot prevent someone from sharing the unique URL, there is a meeting option that allows only one device/connection from each unique URL. You can find the option (only in meetings requiring registration) under Registration Options --> “Allow attendees to join from multiple devices”.
FWIW, I do not see the multiple device option as part of the Create Meeting options, nor is it returned as part of the Get Meeting API response.
Note … If allow multiple devices is not set (i.e. 1 device per unique URL), if the authorized user joins first they will grab the single slot, however, if they arrive after someone else has used the uniqueURL they will be prevent from joining. We find it important to be clear in follow-up and confirmation emails that the URL is unique and should not be shared.