You'll find in most cases, this is the details provided to it by Transdev via bus open data. If Transdev put the right vehicle codes into their ticket machine codes, bustimes would show more correct details.
If you took a moment to jump off the trend of slating bustimes, you will notice that even Transdevs own website has the information wrong. So it's not just a Bustimes issue, it's all caused by whatever codes are in Transdevs ticket machines which is sorted by their depot staff.
(screenshot from Transdevs website for the 21 which shows AD24ZEB tracking on the 21
https://www.transdevbus.co.uk/the-harrogate-bus-company/services/21/)
The eCitaro reappearing was because this was the last known vehicle which was using the 'DEMO' ticket machine code. That details are then kept in the database and reappears when that vehicle code next reappears in open data.
Bustimes can and does handle duplicate registrations.
Bustimes does not interact via Facebook. The group set up on there is merely a fan group and is not actually linked to Bustimes in any way, shape or form. Bustimes only community page is the Discord (and this is linked on the website) but you can also contact them via Twitter/X or email for other issues.