That’s a comment from OC 3 mounth ago.
I can tell you how to bypass some checks, but then don’t expect support from OC when things break for using an not officially supported version.
Noone wants to have a broken instance of ownCloud, and since this is mainly ownCloud’s responsability, it’s ownCloud the one ensuring that it works without mayor problems with PHP 7.3
As stated, there have been delays with the PHP 7.3 support for several reasons. It sounds more reasonable to have an stable product and then enabling php 7.3 with confidence than just enabling the support on a messy product to increase the mess.
If you’re interested, you can check the versions released during that timeframe and the changelog of the releases.