Its not accuracy, its more to do with tolerance to noise, after all you will be switching many amps,
to get an RC on the time scale of 60 seconds, either needs a very big resistance, which is susceptible to noise, or a very large capacitance which is generally price or size constrained out.
If you wanted to go with a single RC, you could accomplish it with a dual op amp. the RC charges off its supply, the first op amp when the threshold is reached switches high, you would then AND this via a transistor or mosfet, to combine with the Pi.
the other op amp acts as a differentiator, when the pi signal falls low, it switches a mosfet which drains the RC back to 0, enforcing the timeout
I will again stress that such a circuit can be sensitive to noise, to keep the RC part well shielded.