I was not aware of this limitation, but this is troubling given what I just mentioned in another thread; that auto-tunnel cuts much closer than pulling terrain around a pre-existing track. The fact you can't get the same ride scenery by placing the blueprint that you could when making the original seems to undermine the concept of blueprints. Though I presume there's some reason that there's this difference between "clipping zones" between terrain pulling and auto-tunnel.
Sounds like auto-tunnel of track on blueprint placement should really be a thing, either way.