I would have to assume though that if it takes 20 minutes to ramp to mashout temps... so 153-168F, that it would take nearly 40 minutes to ramp from a protein rest to sacc. rest. That to me seems like it would be very long. It would no longer be a step mash, but simply a ramp mash.

Again, if you have a direct fired RIMS you have more capability than the guy heating with 5,000 BTU in a little RIMS heater. You have what, 60k or 100k BTU at your disposal? Of course it takes him 20 minutes to mash out, the math supports it, it has nothing to do with his PID or any other variable. You have a finite ammount of heat introduced and a HUGE thermal mass to change.

How many BTU is a stove top? 9,000? How many of you can reach a boil on a stove top with 5 gallons? Now take his 5,000 BTU in his RIMS heater and try increasing the temp of a 7 gallon mash.

Direct fire, or infusion is about the only way to have a short step time. Though, back to the OP, 20 minutes is normal with 5,000 BTU at your disposal and should not affect the beer.