You mean an up-to-5% increase in capacity, and slightly decreased weight, depending on the product?

The truth is that the product with the 16% reduced capacity (Switch 2 Pro controller) is 7g lighter and the one with the 5% increased capacity (Gamecube controller) is 5g heavier.

Besides those two, the general idea is that the capacity is the same with 2-3% extra weight.

Some of these are no change because the existing versions already have pretty user replacement friendly batteries. The JoyCons for example already use the hard sided cells with plugs so I'm not sure what the change will actually amount to. If I had to guess it's maybe to change the glue or method of holding the battery in place to satisfy the ease of replacement requirements.