This is one of the horrible grey areas in instrument procedures. Once you have departed from the procedure to carry out a circling approach, you have, to all intents and purposes, thrown the missed approach away - at least the inherent obstacle clearance protection.
Not all circling procedures are equal as far as obstacle clearance areas go. FAA TERPS circling areas are significantly smaller than those designed to PANS OPS, and will be found in Japan & Korea as well as the US. Getting from a rejected circling approach back onto the missed approach segment is where you find limbo land.
The position of the MAPt in relation to the airfield could be critical.
Circling approaches probably offer the best(worst?) opportunity for CFIT. Be careful, very careful!