Purgatory was not a waiting place - Paradise served this purpose before Christ Jesus came into the world. Then Christ Jesus teaches us about heaven and hell, no more purgatory anymore...it never existed in the Bible
While I do not consider the doctrine of Purgatory to be as assured as others, I can understand how it may be based upon Biblical doctrines.
While Christ died for our sins, we also know we will be tested by fire and all the wood, hay, and stubble, will be burnt up and we will be refined as gold is refined from dross.
Does that process occur after the Rapture prior to the Wedding feast? Or is that a process which must occur prior to our entrance to heaven? To die from the body is to be present with the Lord, so is this another holding pattern until the Final Judgement or at least the bema seat?
I haven’t studied the doctrine that closely before, but can understand how it may have been developed.
I find it odd that you accept the "third state" where those not condemned to hell waited for the coming of Christ, but you can't accept a place of purification before you enter heaven. Revelation 21:27 Nothing impure will ever enter it, nor will anyone who does what is shameful or deceitful, but only those whose names are written in the Lamb's book of life.