The reason the birds get stocked when they do is all about being able to get it done and keeping the costs as reasonable as possible. Even though I agree it would be nice to do it in a way as to avoid the truck followers but in all reality it just isn't possible.
With all of the birds getting stocked in nearly every county of the state each week of the season coming from just two game farms those game farms become extremely busy places. The Game Commission food and cover employees are assigned a day between Tuesday and Friday when they are to arrive at one of the two farms to pick up birds. The crew will usually be there when the farm opens at 7:00 in the morning. Often they have spent two or three hours on the road to get there when the farm opens. I know our Elk County crew usually leaves here at 4:00 am on stocking day. Once at the farm they will first unload any crates they are returning. That might take close to an hour for just two guys.
Then they help catch and crate pheasants until they have the day's allocation all crated. Then each crew gets the number of pheasants they are allocated for that stocking. They have to strap them down and start the journey back to their home county. That is going to take as much as three hours if they are one of the counties a long ways from the pheasant farm. So generally it is going to be noon or so before the pheasants are even back to the county where they are going to be stocked. Often the truck picking up the pheasants at the farm will have birds for two or three counties, to help save on the cost of sending a truck and crew from every county. So, when the truck arrives at the meeting location the smaller trucks from the surrounding counties will meet the larger truck there. Then everyone jumps in and gets the birds for the surrounding counties sorted out and loaded on the trucks traveling to those counties so they can hopefully get their birds stocked without a lot of excess overtime.
Then, at least in Elk County, they will split pheasants off onto three other trucks or trailer, usually to the pheasants Forever crews, to head to some of the harder to reach stocking points. That helps to get the birds fairly and equally distributed to the various hunting areas. That also cuts down on the overtime costs accrued to the Game Commission and the pheasant program.
By the time the first birds are hitting the ground it is generally between noon and 1:00 pm and it is usually between 3:00 and 4:00 before the last one is stocked and all the trucks are back at the crate pick up point. At the pick up point all of the crates are loaded back on the big truck and strapped down so they can return to the crew headquarter and be ready to start the process all over again next week.
Generally on stocking days a couple of that crew are going to have a long day so stocking is something that is done in a manner that gets the birds out there for the hunters but also keeps the costs as reasonable as possible.
As for truck followers. Many of them us a process of elimination. They know they are coming some day that week so if it didn't come yesterday maybe it is today, if not today if must be tomorrow. Other have a call system in place where as soon as someone sees the trucks coming through a certain town they are on the phones to their hunting buddies and they are in the fields before we get there with the birds. It is hard to eliminate some of those issues but we do our best to keep it within reason.
As for doing it on a Sunday. Well that would mean overtime pay for about the entire Game Commission crew at both the farms and those going to get and stock pheasants. That would drive the costs of the pheasant program right out of the feasibility of keeping the program in existence.
All in all the pheasant program is pretty good as it is even though it isn't perfect. You could perhaps make it better by working with your Land Management Officer and volunteering to help with the local stocking program. I know that has helped with a better program in this area.