I wont "bash" the BL Touch outright. If it is used correctly (which it sounds like you do, Paul), it is a useful tool. The problem comes from those that expect miracles from it.. LOL
I have used mirror tiles for years, starting with my first printer, a Solidoodle 4, that was purchased used. It was suggested in Soliforum to help level out the warped aluminum beds they invariable develop (too thin) - and it does work - to a point. There comes a time, however, that the thin aluminum needs to be replaced - and I have done so on both of the SD4s that I have - but I still use the mirror tiles to print on. It was just a logical extension to use them on other printers as they were obtained & built.
I will say this -- I do not remove the mirror tile from my printer - unless it is getting replaced for some reason. I stick it down to the aluminum bed with hairspray and it stays there until it needs to be replaced for some reason. So far I have only had to replace one due to a chunk being taken out out of it with a print... never had one crack on me - knock on wood. I also recently replaced one simply for aesthetics when I updated a few other parts recently - it had spots of the backing coming off - not really sure why, or what was causing it, but it had been in/on the printer for well over a year.
To clean, I use Windex & a single edge razor blade to remove any chunks of stuff, then wipe it down with a paper towel... respray with Aqua Net (covering/blocking motors & fans) and am good to go again for many prints. FWIW, 99% of my printing is done in ABS - I very rarely need to resort to ABS juice to get good adhesion.
My FT-5 is a first generation and has the dual motors. Can't say I have ever had a problem with the 2 sides getting out of sync with each other, tho. It is currently set up with the CNC add-on kit (that was kind of a disappointment, tbh) so it doesn't get a lot of use right now. one of these days I am going to stick the hotend back on it. Just been too busy with other things.