Personally, I think the sight rail was a holdover from BSF after HW bought them out.
The trigger block change was I believe (a) primarily because of machining difficulties - which raised costs from damaged parts, (b) desire to lower costs anyway, as the 85 was competing directly with the 80. The “tile” system removed the problem of poorly threaded cylinders (and the associated cost) and reduced the cost further from cheaper manufacture, allowing increased sales of the 85/95 at a lower price while leaving the 80 as the upmarket option (especially in unrestricted markets like the US).
I imagine ditching the raised rail (once they ran out of BSF parts, or the BSF machinery wore out) was again to reduce the cost of making a rail and a special piston, relieved to work with the rail.
Honestly, I understand the business rationale behind those sort of decisions.
Pity that when HW bought BSF, that they didn’t keep making the B55, just with a Rekord trigger, even if held on with “tiles”. That would have been awesome.