Response to the Gospel is not dependent on the words spoken, it is dependent on The Holy Spirit quickening to the hearer that which He has imparted to them. No one has doctrinal perfection. No one has 100% infallible interpretation of scripture. Some have more than others, but God uses His Word as He wills, not as the preacher wills.
The context of the passage in Revelation 3:20 is a message to the churches, i.e. the saved. Context is important. Otherwise, one could just cherry-pick verses and string them together, and make up any doctrine they wish. That obviously has taken place. The true test of any doctrine is not "does it hold together?", but, "is it faithful to the whole of revealed scripture, when viewed in context?"
God caused revival and a harvest because He willed it, not because it was Spurgeon or Edwards preaching it. You're trying to hold the preacher responsible for the way he wields the sword, rather than realizing that it is the sword that does the work.