My opinion is that you shouldn't under-torque your brake levers, regardless of whether they are cheap brake-only levers or more expensive shifter/brake levers.
I bought an e-road-bike from a shop where the mechanic instructed that the holder for the bike computer should be under-torqued to protect it when crashing. The same holder was the holder of the front light. As a result of that, it was impossible to permanently align the front light for optimal visibility and no blinding oncoming traffic. Every time I touched the computer, I messed up the light adjustment. Then I torqued that bolt to the correct torque, carefully aligning the front light. I have never after that had to re-align the front light.
After they did the first service to the bike, I started riding it again and soon after that found that one of my brake levers was misaligned. I hadn't crashed and I'm sure nothing other than my hands touched the brake lever. At home, I realigned the brake lever, finding it was very easy to turn, so easy you could turn it accidentally just by riding the bike. Then I checked the bolt torques and both levers were under-torqued. I was certain that during the first service, the mechanic thought to "help me" by under-torquing each and every bolt on my bike.
I tightened those bolts to proper torque. I have had never again to re-align the brake lever. It stays in the current position.
The problem with under-torquing is that if you under-torque by little, vibration is going to slowly loosen the bolt. You will have to re-torque the bolts to a too-low torque every 200 km or else the part will be completely loose. On the other hand, if you torque properly, vibration will not loosen it and the part stays attached and in position forever.
I no longer use the services of that particular bike shop. Not only because of the under-torquing problem, but also because the bike shop seems to use Park Tool Allen keys that have a ball-end and a normal end, and the bike mechanic seems to do all the tightening with the easily accessible ball-end using the large handle in the tool, not using the normal end at all for final tightening. I personally think that Park Tool has caused a lot of damage for great many cyclists by making tools that allow easily applying a lot of torque using the ball end. The ball end damages bolt heads in such a manner that they won't anymore take an Allen key that is a tight fit (and the tighter the fit, the better, because tighter fit damages the heads the least).
It's true that combined brake/shifter levers are expensive and fragile. But so is your time. Checking adjustment and re-tightening bolts to a too-low torque every 200 km costs a lot of your time. The solution to brake/shifter levers being expensive and fragile is to use brake-only levers and bar-end shifters. Unfortunately, we can't do that anymore since modern hydraulic levers aren't available without shifting function.