I read your link and it does not support your view that the facts are different than they appear. He calculates a bit differently (including not just currently living bats but those bats yet unborn) but still I feel the tunnel was not necessary
You're looking at someone saying "look at this tiny pothole and how awful it is on a road" when 50 yards further down there's a massive chasm.
It's a distraction technique as old as the hills, and implies the blame for the missing 100b is because of bat boxes, while others run off with the remaining 99b.
No it's not. The bad boxes are both literal and metaphorical. There are many stupid straws on this stupid camel and every stupid straw is there because a stupid person said "but what about my bats, or whatever" without consideration and/or caring for the big picture.
When this one comes up I always point out it would be better to not bother with HS2 and spend the money on making it easier for people not to have to travel around.
Great, but it's also a goods corridor; the only way around both of those at the same time (absent massive depopulation) is to move the people, would mean building loads more houses.
The WCML is perfectly adequate for that. HS2 is a vanity project for business and general passenger travel, none of which is certain or impossible on the WCML already.
But the WCML is at capacity, so it is not in fact adequate.
"There is no available capacity without significantly impacting performance and
causing a reduction in timetable resilience due to the resulting requirement for
successive services to run on minimum headway"