We were fully aware that mere coincidences are possible and that speculations based on them can easily drift to the non-scientific domain of numerology, especially in the field of units of measures, where the large number of units through the ages and around the world cover almost with continuity the range of lengths in the human scale. Therefore, we were searching if there were reasonable explanations for the close coincidence pointed out in our question.
A physical reason is ruled out. A unit of length defined as a fraction of a planet meridian makes the period of a unitary pendulum only depending on the planet density. But this period has no connection with the planet rotation period, and then with its 86400th part.
The suspicion remains -- definitely strengthened -- that, among the possible choices of Earth related units, the choice favored the one that approximated a pendulum that beats the second.