The DWP only says don't send by recorded delivery because they don't want to have to sign for it. Plenty of people have been grateful for doing so when the DWP has tried to claim that their forms were not delivered and they have the proof of when it was signed for.
People have to do what they feel is best or what they can afford. The important point is to have some proof if anything goes wrong.
BIS
Nothing on this board constitutes legal advice - always consult a professional about specific problems
