I have always felt that the Strip was Las Vegas Blvd (only) between Sahara and Tropicana Streets. The Stratosphere was too significant an addition to not be included effectively extending the strip. Mandalay Bay replaced another casino which had always been regarded as a strip property. So Mandalay Bay to Stratosphere is my definition of the strip.

The others like Hilton, Hard Rock, Rio, Palms etc are "near Strip", but are not strip. I expect the lines to become even more blurred when these properties like the one replacing the Boardwalk open.

I can see the "property" being on Las Vegas Blvd, but the actual hotel/casino being off strip. UNlikely I confess, but you never know.