It's rather more than that, the details do not have to fit hands, the matter of eyes does not come down quite to fits.
The "coarse" similarity of merely "having" handles, shafts, and dials is not exactly the point. It's very strong similarity of appearance in details.... Almost as if some of the parts were made by one maker and used by several.
Perhaps the appearance was made so similar (almost identical) to avoid GIVING anyone "fits".... So that none of them really looked different or "strange" compared to the others, and a user would feel instantly at-home no matter which was at his current place of employment.
In any case, some of the parts look almost like "catalog parts", they are that close in appearance, and design.
Safe bet they ARE "catalog parts".
Yet-today "balanced lever" with a crank , tapered cross shank, and ball counterweight, opposite end, and round handwheels come from speciality makers.
So do machine slides, Gits Brothers oilers, Bijur lubricant metering goods.. roller bearings pulleys, gears, fasteners, "etc."
Much the same as BMW & Mercedes buying nearly identical seats from Recaro, window cranks and brakes from ATE, steering gear from Getrag, transmissions from ZF, air-suspension from Bilstein, "etc."
LeBlond began as a components supplier. So too, the Dodge brothers and their "Motor Parts Company" --> MOPAR. BirdPort mills began as add-on heads, then grew themselves an ass of their own design, later.
MOST companies buy-in all the simpler parts, have others made to their spec, only make the "core differentiator" components under their own roof and direct supervision.
Cannot
survive, economically, if your scarce resources are trying to beat an industry-dominant volume maker of ignorant setscrews, taper pins, Woodruff keys .. knobs, hand levers, and handwheels... just to claim "we make all our own parts".
"All our own parts" got a still-young Herr Pelz three days in Kaiser Bill's Aerodrome guardhouse on bread and water, only, closing months of War One.
His wife had relatives in Austria getting cigar-lighter wheels and flint mechanisms to him. In between servicing Richtofen's old squadron's Mercedes six aero engines- the ones he had been the factory fitter "gang leader" for as-built - he had a side business mounting the lighter-works atop salvaged
(eg: "stolen" rather than sent-off for reloading) War One Hebel Model 1894 signalling-flare "pistol" brass cartridge cases. And the 26.5 mm Hebel wasn't exactly no concealable "pocket pistol", neither!
Ran short of brass cases to fill an order for lighters.
That close to the heavy guns of the front lines as short-range aircraft of the era were based, he didn't think anyone would notice the noise atall if he fired-off three more to finish out the "standard parts" needed ... instead of waiting for "normal consumption".
"Noise" wasn't to be the problem. He got THAT part right!
What TF would a Master Machinist drafted to fill a shortage of front-line aero-engine mechanics know about the VISUAL effects of Aircraft-control signalling
flares?
Bet your sweet ASS it was "noticed"!
Hadn't have been the best mechanic the squadron had, prolly have gotten his ass SHOT!
Pays-off to be good at yer craft. Can even save yer ass from the consequences of some of the
damndest foolishness?
Or so we hope and pray, even yet today?
Guess you'd just have to know Machinashitists and "risk-taking"?