Using two woofer to cover the same frequency range is neither inherently good nor bad, it just depends on what the designer is trying to do.
Compared to using a single woofer, using two of that woofer to cover the same frequency range lowers the distortion and power compression for a given SPL because less excursion is required along with less power, but you need twice the box volume. Assuming both woofers are facing the same direction, the radiation pattern will be considerably narrower in the plane where their center-to-center spacing is the greatest (for an MTM, that would be the vertical plane),. Whether or not this is a good thing or a bad thing depends on the rest of the system design.
Recently I designed a speaker where one of the goals was to reduce the amount of energy in early reflections via fairly aggressive radiation pattern control. The best constant-directivity waveguide I could find for this application had a pattern 90 degrees horizontally by about 50 degrees vertically. Using two midwoofers covering the same frequency range was the best way to get the directional control I wanted along with good pattern-matching in the crossover region in both the horizontal and vertical planes.
If my priorities had been different, I might well have used just one midwoofer.
Duke