Exactly. Here we have those who would admit that there is no way one can tell who is regenerate, or who is not. Yet they want to examine the wool to determine if they are, then to baptize them only if they meet some criteria. You know, let's see just how spiritual and scriptural this brand new believer is. Afterall, they better be doctrinally sound, clean, knowledgable, pure and holy, and then, since they've earned it, I'll baptize them. What a load of bunk and it is quite Pharisaical, not to mention unbiblical.
Yes, I'm certain some can muster up some hypothesis, or some other situation that is meant to throw some wrench in this, but none of this reason supplants or transcends Scripture. It just goes to show man will argue his reason against the Word of God.
Nowhere in Scripture was there this waiting period. Simply, they preached and those who believed were baptized. They weren't examined, they weren't sent to a class to make the preacher happier in conscience for baptizing them. To do so is to practice religion and Pharisaism, not Bible. Instead, in the Scriptures, albeit imperfect, they were simply believers, and they baptized them as instructed.
We clean up our act after salvation and after following in obedience the command to be baptized, not prior to either.