Not sure of your direction on this with the reference to 'finger ports' but just to be clear we're not talking open port vs closed port here.
Factory bottom fed design on closed port transfers has been common practice on many models of very high revving/high output saws, more particularly with quad ports but there are also many examples done in dual port configs. Some were even factory recommended 'performance upgrades' that were implemented by dealers on new saws.
This is nothing new...
I don't see this as something that would significantly move the peak torque down in the revs, though that it adds a bit more crank case volume may have that effect to a degree.
You could also look at this mod as feeding the lower transfer in a more direct/uninterrupted path rather than having to convolute in from the side through the piston windows. Six 'o one, half doz 'o the other...
Yes there are some new flow dynamics but the entry and exit angles of the uppers remain largely unchanged.
You flatter me with your suggestion that there may actually
be a direction to my spontaneous analytical musings.
Finger ports.
My introduction to chainsaw engines was entirely through the window of Husqvarna's Australian 1983 model range. As an EMAB subsidiary, more brands kept appearing on our sales & service inventory. First Partner, then Poulan & Pioneer came on board, each expanding my knowledge of the diversity of design concepts.
It was Kevin Murray, then Pioneer's design engineer, who used the term "finger ports" to describe right-angled ports cast into the cylinder sides and rear by means of retractable "fingers" on both the inner dolly and the outer mould from beneath the cylinder base.
This is not the same as sand cast bottom fed quad or dual ports found on Husky 480, 372, etc.
as you describe, so I agree with your first paragraph.
Re your second paragraph. On reflection, I was probably trying too hard to find an explanation for the subjective impression that the non-original piston saw performed better, when in all likelihood, no definable explanation exists.