I do think it might be better to let the later conscript armies have more free deployment as they weren't coming based on a pre-planned mobilization, but the regular armies that show up as reinforcements had plans and timetables and a PP cost to redirect them is fairly reasonable.
Exactly. If you want to talk real world, countries have mobilization plans. If the Whatever Army has its mobilization plan to assemble in and around Stalino by 20 days after they are called up, then you can't just tell those 120,000 men and all their equipment to instead assemble near Luga. They are going to assemble at Stalino. The trains have been ordered, the equipment is in its stockpiles, etc., etc.
Yes, at some point the new conscript armies that are being pulled together from scratch, with no prior planning or equipment, can be, as much as possible consistent with transportation, assembled where you want. But even then, telling then to assemble in the middle of the Pripet marshes is not going to work. Also there are limits on changing your mind. When you have 100,000+ men, hundreds of artillery pieces, millions of rounds of ammunition, uniforms, vehicles, rations, and such can't just be moved from where they are assembling to somewhere else easily. If you started the process in Minsk, well, you pretty much have to finish it there too.
The Germans may have been a lot of things, but they were not ignorant of the facts above. There were really only so many places with the infrastructure to serve as marshaling points for new troops. They were unready for the seemingly endless supply of troops the Soviets could muster, so it might be something to think about modeling in some way.
Just my opinion.