Mike,
On a IFR flight plan, VFR tower controllers receive their departure headings that they issue to you from the controlling IFR facility. As for being cleared to land prior to the runway being clear, that is called anticipating separation, and is legal within the 7110.65. Phraselogy being laxed, just like the U.K. we have specific phraselogy that we are required to use, as with pilots, controllers can develop poor phraselogy habits too, which when the facility undergoes a evaluation will be corrected.
Mike
NATCA FWA