When engis reclaim on attack or patrol move, they stop between reclaims.? Engineer reclaims, does nothing, reclaims, does nothing, reclaims etc? While on manual reclaim they reclaim, reclaim, reclaim etc. So even when not considering advantage of choice of order on manual reclaim, manual reclaim is faster as long as player has apm for it.
Advantage in the beginning of the game can snowball into big advantage, it is not so important from what rating exactly people have necessary apm in average. It favors click spam like some game on smartphone where you do nothing but click as fast as you can. No tanks, units, nothing but clicking.
I can understand consideration of gamespeed. And at some extent the added complexity of new command. Althought having extra command seems easyer to learn, than to learn how to spam hundreds of clicks very fast.
There is also possibility to modify actual attack move/ patrol. Removing that "do nothing" part should make it more effective. Without negative effects. Drawing a ring, or corridor of effect when placing it could make it easyer to learn and make it more "moderne" (maybe with option to remove it). And then placing shift attack moves( as some players do), would cover an area. There could be a reclaim choosing inside the actual reclaim circle/radius, eventually. So that engineer chooses higher than x mass reclaim before the small reclaim. But only around itself in the limit where it does not need to move to get it. So that althought it adds some calculations to game, it would be always very limited. Eventually recalculated when engie moves and stops on attack move. This also should add effectivenes, with minimal performance setback.
I would like the option, that engis just stop, when mass bar is almost full, rather than running into unbroken trees, but this is kind of out of the scope of this discussion...