Most arguments against seem to be that manual reclaim isn't that important (in terms of helping you win the game). If anything, that's another argument for the change (since it's not going to have much of a balance impact)!
I'd bet most people playing the game find it more fun to do things other than playing 'click rock not tree simulator'. Something that therefore reduces the APM required for manual reclaim (and therefore the need to do this) is likely to increase fun for such people. The change also removes a source of frustration with not being able to properly execute a decision - as mentioned above, if you want your ACU to reclaim an area, there is no suitable option at present. Unlike engineers, you don't have a sub-optimal attack-move order option, and if you do patrol then that can cause various issues/unintended consequences. It is also still sub-optimal to choosing the reclaim targets yourself, just not as sub-optimal as an attack-move order, so people wanting to eke out small advantages that make use of higher apm will still be able to.
So we have a mechanic that isn't fun, can at times be frustrating, and seems generally accepted by proponents of it posting here to not result in a decisive difference between games being won or loss. Other than this mechanic rewarding people with high APM, what's the benefit of banning a reclaim brush type option?
Also, why is it acceptable to automate/reduce apm with features like mex capping and mass fab automation, but not with reclaim?