The NIL/Portal convergence has turned things into a kind of a free for all. I came across this old article about Tennessee's reaction to Nico leaving. This is the only written piece where I've seen it referenced that a school tried to lure away a player that was not in the portal.
It must be common and accepted, given that the article treats it that way.
"The Vols tried to lure TCU quarterback Josh Hoover to Knoxville and contacted his representatives last week, but Hoover rebuffed those overtures to stay with the Horned Frogs, a source briefed on the discussions confirmed. The Fort Worth Star-Telegram reported that the Vols offered $1 million more than the seven-figure salary Hoover was making at TCU."