I'm slightly confused, perhaps we are misunderstanding each other. The Tesla app shows the sites you can use and operate as a non-Tesla owner. That is some Tesla sites not all, plus the EV OTM sites. Showing sites that you can't use, i.e. the Tesla only sites would be pointless if you don't own a Tesla. You only use the Tesla app if you want to find and use a Tesla charger.
There are basically three types of EV charger apps.
1. Charge network specific. Such as the Tesla app, the Gridserve app, Instavolt app or the Ionity app etc. These show you where their chargers are and you can use them to control the charging.
2. Multi network cards. Such as Electroverse, Zapmap, Shell that show you all sites, and also the ones that they can control for charging These can be used on most sites all over Britain and Europe for most networks, particularly Electroverse.
3. Apps/webpages that show all chargers of any operator, used for locating chargers only such as Charge Finder and Chargemap.
Apologies if I have misunderstood what you are saying and have oversimplified this.