If you don't trust the Mazda main dealer to change oil on the Mazda without knowing torque figures (?) why use the main dealer to do it? You could do it yourself or give the torque figures to a local mechanic and insist you watch him using his torque wrench.
Because my own experience with 'trusty independents' is likewise the same. Which is why I go to Mazda (or other dealerships with other cars), as I find if an issue arises they are more 'official' at dealing with it. I've found the 'trusty independent' akin to a 'trusty Roofer' when things don't do to pan. The torque figures weren't for 'normal' oil, but a gearbox oil change, when I thought they don't do my particular car that much, and it's known to have a chocolate gear box. I actually brought my own oil that day, as the word is that dealers stick in whatever (Mazda UK weren't that much better when I was tying to get part numbers for the OEM gear oil). They were fine with that, but it transpired they use the OEM oil, as he showed me it!
I can't do it myself as I'm useless.
Essentially I'm an outliner: I'm well into car detailing so don't really want any one messing with it, and cars are my hobby. 99% of people who go to dealerships and even 'trusty independents' are the types who aren't really into cars. So people get used to working certain ways, for the 99% of customer.
I once heard someone say something which stuck with me, along the lines of that in life, people don't really deeply care, or listen, when it;s something which isn't personal to them, so if it's personal to you, you usually got to be a pain in the a**e, or make them think you're an obsessive to get someone to listen to what you want, and expect, and up their game.
And as I've said in places before 'how many people do you see like me' (usually zero or the odd one)? So my argument is it isn't really that hard in a job to be totally focused on a job once a year. Even more so when that person is given them a decent amount of money.
Also, if someone don't want to do it, if I'm deemed too 'hard work' (you know, wanting them to do a good job), I actually don't mind that, as it says to me they don't think they have the skills to do it anyway.
Like tyres for eg, a nightmare in general. How many times I've gone in with PRISTINE alloys, not a mark on them (as in not a micro dot), busting my gut every week with ph neutral wheels shampoos etc, to see 'fitters' mark them,-. The arguments I've had. Like how can you fit tyres for X amount of years and still mark someone's tyres who's alloys are pristine and in front of you the customer's saying they're his life.