At last night's referees meeting the law changes were explained by a Level 6 referee who had had the full RFU briefing.
I asked: "Scrum just iust in Red's half. The referee awards a FK to Red. Can a 50/22 be used?"
Answer: No. There must be a phase of play first.
Which just proves that anyone get it wrong: the RFU Clarifications include:
RFU "Would the ball from a scrum or lineout with a throw in on the half-way line qualify for a 50:22, whichever side wins the ball?"
WR; "It would depend where the ball emerged from the set piece. If it were in the half of the team winning the ball, then 50:22 allowable. If they had pushed their opponents beyond the halfway before it emerged and then passed it back to within their own half, then 50:22 is not allowable."
Not a single mention of "a phase of play". Some attempted simplifications just serve to confuse people. Just use the Law wording + grammar clarification:
"Either the team did not take the ball into their half, or [if it did] a tackle, ruck or maul took place within the half, or an opponent touched the ball within the half. This variation does not apply at a kick-off or any type of restart kick."
The WR explanation also demonstrates that the halfway line is included in both halves of the field of play!
BTW - I don't put it past WR to change their mind (again) at some stage!