What's right and wrong in this?
Not easy to answer, but I've another opinion for you
I could imagine, the "helicopter guys" claim a turboshaft engine in a helicopter has a higher BPR than the same engine fitted in a fixed wing aircraft and i agree in some way with them, even when most of the "bypass air" is used for lift and not for propulsion.
An example to make this more clear would be the Bell V-22, the geometric of the engine doesn't change, even if it's tilled up and the V-22 flies like a helicopter.
Of course it's very unusual to claim, turboshafts of a helicopter have a high BPR.
The amount of thrust produced by the hot-section can differ from engine to engine, on a low BPR engine it maybe more than the cold stream, on some turbo props the residual thrust amount is very low. (the RR Tyne MK22 delivers ~4200kw shaft power with a residual thrust of 5kn ).
Drawing the line between low bypass, high bypass, ultra high bypass and props isn't easy, I've some literature in which is a low bypass: ~2:1, high: 4-9:1, ultrahigh for UDF's 12-15:1 (or maybe more) and props up to 1:40 and even more.
Important for the usage, of which BPR where to install, is the operating place and for fixed wing aircrafts this means the operating speed. As you know, with a higher the bypass the engines work more efficiently but this can't be spread to all kind of A/C, the exhaust speed is also important (an A/C can't fly faster than the exhaust speed) and along with this goes the pressure ratio of the bypassed air.
So a "mega-bypass" like a helicopter would accelerate a lot of air mass with a more or less low speed, a prop accelerates less air mass but to a higher air-speed (the "thrust" or the needed shaft power might be the same) and a turbofan does even less air mass with higher air speed and with a certain fan-pressure-ratio. This pressure is converted in the nozzle to additional speed by reducing the pressure to approximately average air pressure (this ensures, that the engine operates efficiently and the exhaust gas flow doesn't spread up after leaving the engine ).
Thats also the reason why fighter jet engines with afterburner have a reduced BPR but with a higher fan pressure ratio than commercial A/C's. So turbo-props work fine up to ~M0.7, fans high BPR up to ~M0.95 (or little more) and above this speed a low BPR engine would be the choice,
AFAIK the Concorde was able to fly supersonic with afterburners off, once reached supersonic speed.
rgds