...the run time forces you to stick to a strict schedule, putting stress on you during critical tasks such as gas switches.
Another perspective... the stress of following basic tech procedures on a strict schedule is a diver-originated issue. i.e. task loading versus ingrained skill
It never made sense how you're supposed to carefully check your gas and depth and do a switch at the same time you're rushing to meet the schedule planned by your run time.
1) Most dive planning software allows you define extra time, within the run-time, for completion of gas switches. Or you can manually add that (slates). This works if doing 'team switches' using formal procedure (NOTOX) once reaching the deco level.
2) Many technical divers prepare for the gas switch during the 'free-time' on ascent to the stop/gas-change. This basically re-orders the NOTOX protocol;
on ascent to stop - confirm the tank/markings, deploy the regulator, turn the cylinder on, confirm team mate has prepared the right gas (trace regulator to cylinder and confirm markings)....
on arrival at the stop; confirm above MOD, signal, gas-switch, examine buddy again (trace regulator to cylinder and confirm markings). That is seamless and very quick.
I teach both methods on my courses. What matters is that all critical steps are completed before you breath the regulator... and that a physical/visual confirmation of buddy/team is completed during or immediately after the switch.
Then I moved to IANTD normoxic, and my instructors did away with run time. This allowed us, in team diving, to do our gas switches sequentially, so you can check your teammates switches, and start your deco time only when everyone has switched. So you don't have to stick to an absolute run time schedule planned at the start of the dive.
There is no reason PADI courses can't be run with sequential (or team) switches. But why blow run time, when you can just anticipate your needs in dive planning?
Run-time is pretty useful... and much easier to follow than stop-times alone.
I don't really understand why your instructors would have you plan/mark a run-time, then condone breaking it as a routine. It sounds lazy to me...
It also makes more sense, for instance, if you had to spend a bit more time during a switch, to untangle a hose, or fix a buoyancy problem, which would throw off your run time for the rest of the dive.
Which makes a good argument for planning/preparing ahead... and making use of your ascent to stop, when you have nothing else to do...
So I say, why task load yourself and stress out trying to stick to a run time schedule -- to the point where rushing can compromise safety?
Task-loading and stress is a diver/skills issue, not a procedural issue. It seems like you are asking for validation to abandon a proven, tested procedure, to compensate for personal difficulties you are experiencing.
You WILL find the task-loading and stress decreases as you gain more experience and competency. Re-visit this thread after another 100 technical dives and you'll see what I mean