I haven't seen the document, but if there is a line it in as you suggest, they I'd say good, very sensible. People massively overreact and political opponents use it to throw stones. Why invite that?
The fact is we would not agree to any deal which is net worse for the UK, would we. Even if we agreed to pay more like US prices on the 10% of the drugs we buy from the US - and I am not saying we would for a moment - then we'd only do so for some quid pro quo which made doing so worthwhile. So overall, we'd be better off. And if the NHS's drugs bill was to go up by say 10% (a doubling of the US drug costs) then we'd have to bung the NHS more money to pay for it, which would be possible because of the better overall trade deal we had got. If the trade deal is not sufficiently better, we would not agree to it, would we.
So there is absolutely nothing to see here. It's either
(a) All complete bollocks, and represents a historical discussion not even being considered any more, and/or
(b) Perfectly reasonable and sensible.
Shit-stirring and scaremongering from a desperate Corbyn thrashing around on the rack of a -12 point polling gap.