"As Joshua withdrew from the armies of Israel to meditate and pray for God's special presence to attend him, he saw a Man of lofty stature, clad in warlike garments, with a drawn sword in His hand. Joshua did not recognize Him as one of the warriors of Israel, and yet He had no appearance of being an enemy. In his zeal he accosted Him, saying: “Art Thou for us, or for our adversaries? And He said, Nay; but as Captain of the host of the Lord am I now come. And Joshua fell on his face to the earth, and did worship, and said unto Him, What saith my Lord unto His servant? And the Captain of the Lord's host said unto Joshua, Loose thy shoe from off thy foot; for the place whereon thou standest is holy. And Joshua did so.” 4T 159.1"
"And he said, Nay; but as captain of the host of the Lord am I now come. And Joshua fell on his face to the earth, and did worship, and said unto him, What saith my lord unto his servant?"
EGW directly quotes and elaborates on the Joshua passage, making it a clear explicit allusion.
The glory of God hallowed the sanctuary, and for this reason the priests never entered the place sanctified by God's presence with shoes upon their feet. Particles of dust might cleave to them, which would desecrate the holy place; therefore the priests were required to leave their shoes in the court before entering the sanctuary. In the court, beside the door of the tabernacle, stood a brazen laver, wherein the priests washed their hands and their feet before entering the tabernacle, that all impurity might be removed. All who officiated in the sanctuary were required of God to make special preparation before entering the place where His glory was revealed. 4T 159.2 It was the Son of God who stood as an armed warrior before the leader of Israel. It was the One who had conducted the Hebrews through the wilderness, enshrouded in a pillar of cloud by day and a pillar of fire by night. In order to impress the mind of Joshua that He was no less than Christ, the Exalted One, He said: “Loose…
"And he said, Draw not nigh hither: put off thy shoes from off thy feet, for the place whereon thou standest is holy ground."
While EGW doesn't directly quote Exodus 3:5, she connects the command to remove shoes with the holiness of God's presence and applies it to Joshua's encounter with the Captain of the Lord's host, drawing a thematic parallel.