5000' is in CTA, the 4500' step goes out to 20 DME. I think procedures designed at controlled airports are designed to stay within CTA - someone with more qualifications may be able to help here. Obviously not a consideration when airspace is deactivated though.
I have to agree with Bingle, why descend to 5000' and mix it with the weather and terrain? I always briefed we would hold at 6000 minimum if required due to the DME and speed limitations at 5000'. You can still capture the localiser and glideslope comfortably from 6000'.