I mean for customers just buying random stuff yes they have issues as you know being a 13 year mechanic.
For a mechanic of 13 years probably not as many issues. I do have some mechanics who struggle here and there but usually because they decided not to do the research. Luckily I am a gear nerd so I have been able to help out and find compatible stuff fairly easily. Shimano has the tech docs and SRAM has manuals on their site and maybe more and there are resources like the late great
Sheldon Brown 's website and plenty of other stuff out there on the web plus you have the Sutherlands and Barnetts manuals and Lennard Zinn's Art of ______ Bicycle Maintenance so it should be super hard. You can also do some trial and error sometimes you can get stuff to work. We certainly have done a lot in the shop people said you can't do and it works fine with no issues but that is par for the course at a professional bike shop with knowledgeable staff.
I had one staff member make a claim that SRAM Force was lower than Rival and convinced other people of that but it happens once and while where people are less than informed and they influence people.