Yes, scan does enable the interface ... or rather, it disables it for normal purposes (e.g. AP or station) and uses it to scan surroundings. After scan is finished, the interface returns to its previous state (if it was disabled prior to running scan, then it becomes disabled again).
Yes ... I understand it. But your answer doesn't tell how not to allow scan after wireless interface is disabled, your answer says not to start the scan. But what if the interface was disabled by different admin that the one trying to run scan? I don't see any harm in running scan if interface is disabled (because it doesn't interfere with anything).
But if @atropos89 is actually asking how to prevent wireless interface being used for scanning: by using hardware disablement tool (e.g. soldering iron or a cutting device) to ultimately disable wireless interface.
As always: if software can disable it, then software (could be another piece of code) enable it.
Maybe it is harmless, but it is illogical, the OP is correct in asking that if something is disabled, it should be disabled, when you manually initiate a scan on a disabled interface, in a perfect world RouterOS should throw an error like "Cannot scan from a disabled interface" or similar and reject the command.