I'm not entirely sure what you mean.
What is the supposed "coincidence"?
Yes I can see it would require one to consider the significance of the events.
Consider. There is a Biblical promise that Christ will return and that Christ had more to say unto us, it is foretold knowledge would increase.
There is a tradition in Islam that knowledge consists of 27 letters and that only 2 letters had been released, and that when the promise was fulfilled, the remaining 25 letters of knowledge would be released.
As such, an age of a rapid increase in knowledge was foretold, exactly as as happened since the mid 1800's.
The Bab was the dawn of both those promises and on the day after the Bab made that declaration, the first ever message that opened up this age of knowledge was "What has God Wrought".
Yet even more, the same night of that declaration of the Bab, who's purpose was to prepare the way for another Messenger, who would expand on the knowledge released by the Bab, the Son of that yet unknown future Messenger (Baha'u'llah) was Born. That Son (Abdul'baha) was destined to be the perfect example of that Knowledge and was destined to explain the capacity of that knowledge to all humanity.
Coincidence?
Regards Tony