TL494CN and error amplifier
The intended use of the TL494 is a closed loop SMPS controller.  Error amps are used in the feedback loop to make the output voltage regulated.

 (source: fig.35 here)

On the other hand, you are re-purposing TL494 as a PWM motor controller.  You only want the PWM function without closed loop feedback.  You don't need the error amps, and they shouldn't interfere.  Notice that:


Error amps are connected to the feedback node through diodes
Feedback node is accessible on pin.3.


If you can have the output of the error amps always below the feedback (pin.3), then the diodes will always be reverse-biased, and the error amps will not affect the operation of TL494.

Look at the 2nd circuit in the O.P.  Both error amps are wired as comparators such that V(IN+) &lt; V(IN-) always.  The output of the error amps is always low and lower than the feedback.
That is what is needed.