I think you misunderstand how dynamic range is measured...
Dynamic range is the ratio of the highest signal to the lowest signal level, not the number of absolute steps in between, since it is equally applicable to analogue waveforms as digital signals. The well depth is the highest signal level, whereas the read noise (and any other noise contributions) will determine the lowest detectable signal - but the latter must be distinguishable above the noise, hence why lower noise cameras are more desirable than noisier ones, regardless of well depth.
In the case of our sensor situation, the 294 has deep wells but the read noise is such that it limits the dynamic range to 13 stops (bits)...therefore, a higher resolution ADC is not necessary, by definition. The 294 is complicated somewhat by the HCG mode - it's actually pretty noisy before HCG kicks in at unity.
As in Colin's example above, the popular KAF-8300 may have a 16-bit ADC but is limited to relatively meagre (by today's standards) dynamic range, on paper. That hasn't prevented owners from putting out millions of great pictures with them over the years though
The ASI1600, for example, is capable of a solid 12 stops of dynamic range (at around gain 75)...this is a case where the sensor is indeed limited by the 12-bit ADC...not an ideal scenario, but doesn't prevent effective use. Likewise the 183...even with its tiny pixels, it can muster 12 stops of dynamic range (again the limit of the ADC).
It's probably not worthwhile getting hung up on the ADC issue, as it's less significant that it might first appear.