Filling with solder cannot alter the handoff point ! it can only alter the actual tunnel.
How can it have no effect on that?
The solder doesn't magically just go inside the tunnel and nowhere else, it's on the top of the untented via/pad/trace too, and going over the edges.
If your soldering process is under perfect control it will i deed bulge both top and bottom, but it is not a guarantee.IPC recommends not to rely on that alone. Oversize the hole.
There was an article in PCB magazine a while ago on this. I'm trying to find it.
On large current traces it is actually recommended to drop down multiple vias, creating more handoff area that what would be required. But this is purely because of mechanical concerns. Under mechanical stress the via plating may shear off. Empirical data has shown that the cracks typically happen on the rolled copper to plated copper barrier.
Rolled copper lays horizontally. You grow plating on top and sideways. So the shear point is if you go down in the tunnel at the point where the vertical plating transits from rolled copper to the dielectric material. That is a fragile point.
Again, if you flood it with solder : problem solved. Solder is a soft material and will withstand vibration better than the hard copper plating in the tunnel.
Most microcracks happen during reflow. Improperly conditioned boards, poor temperature control and the via's will popcorn or microcrack.
It is all about long term reliability.
A real pad is self solving due to the component pin and solder fillets.
A signal via (tented) is not a problem
A power via should NEVER be tented so solder can enter and solve the mechanical problem , but do not rely on the solder to solve the handoff problem. You have no control over the end process. As a PCB designer it is your task to make the layout post process independent. So oversize power via's , plonk multiple down , remove tenting. Even if back end screws up , it will still meet requirements. It can only be better than minimum required.
Never rely on back end processing to solve a design problem.