No, there really isn't a lot of gray area. The scenario you've outlined above isn't practical b/c a prospective school cannot host a visit unless the player's school of origin has released him from his scholarship and permitted him to transfer to the prospective school.
Sure, a kid can visit a prospective school without contact with that school's football program, but why would he do that if his school of origin has not approved of it or released him to the prospective school. He can't transfer there if his school of origin says he can't. The rule is designed to avoid situations like a WMU following his coach to Minnesota.
And, no, a transfer cannot call a prospective program to inquire about the availability of a scholarship if the program of origin has not permitted him to do so in granting him a release to the prospective program.
The athlete is free to contact a prospective program in writing to announce his intentions to transfer, but the prospective program cannot communicate back until the school of origin okays it.
Could a HS coach call to find out if there is a scholarship available? Sure, but an informal offer of a scholarship via a HS coach would still be a violation of transfer rules. So if you're going to break the rules, you just a well do between two parties rather than three.