It seems to me you are ignoring the depiction of the southern sector
on
the map view that shows 2800. This applies to aircraft inbound to
DOCAP from anywhere southern.

That sector is essentially a feeder route. If cleared for the approach
within that area, you could descend down to 2,800 if you were above it,
absent any other altitude assignment by ATC.

Many approaches have feeder routes, but you're not obligated to fly
them to the IAF if ATC clears you direct to the IAF and assigns an
altitude.