Here's something to consider;
New brakeshoes never match used drums. That is to say, if you lay a new shoe into an old drum, and manage to not hang it up on the ridge, it will rock up and down the friction surface. This means that the shoe is only contacting the friction surface over a tiny patch. It will take thousands of miles to break-in.
If it's a bad enough mismatch, you'll get extra pedal travel, as the shoes force the normally round drums, into an oval shape, at which time the pedal will get harder and braking will improve, but it may take both feet on the pedal to achieve.
If you machine the drums to restore them to round, this changes nothing, because the shoes are still only contacting in a tiny patch.
The proper procedure to cure this situation, is to take your shoes and drums to an old-school brake shop, and have the new shoes ground to match the radius of the old reground drums. If the drums are excessively worn, then the shoes will have to be excessively ground, reducing their lifespan.