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.
Golly Nobody, does that include YOU?
Some have more than others,
In this case you have more than Spurgeon and Edwards put together, huh?
but God uses His Word as He wills, not as the preacher wills.
So if God uses Revelation 3:20 as a salvation verse (like he did with me) and people are convicted by the Holy Spirit after they hear it, then You're not going to complain, right? And if Spurgeon and Edwards use it to convince people to receive Jesus, then you are not going to call them on the carpet because of the horribile hermenutics, right?
That being said, what is your problem with Revelation 3:20? Its like you are repelled by anyone, including good solid dyed in the wool Calvinists using it to call people to repentance.
Its a call to Jesus verse nobody. God uses it for that purpose. Maybe you should too.