When I was crew, although trained to deal with most things I always found avoidance was the best policy. Just because I know how to do not mean I want to have to perform CPR.
Medicals are not pretty, and if it means someone can't eat nuts for a couple of hours then so be it. The amount of people who eat nuts every day and who will be inconvenienced must be miniscule. Not to mention the paperwork and inconvenience of a divert too potentially.
There must be a risk. Didn't FR recently have an incident of a pax eating nuts causing an anaphylactic shock a couple of rows away despite several PAs to say not to, so much so for FR to ban said pax for two years.
I do think it is important for airlines (I'm thinking UA?) who warn pax that they cannot guarantee a nut free environment. Covers their back I suppose. Who can blame them, especially when you operate within the US and US-UK?
Haha. Yeah 'may contain nuts' on a a packet of nuts or 'caution may be hot' on a coffe cup - what a world we live in.