I would just do as HO ask. And even in the unlikely case they refuse you, you have written proof of what was asked and will be able to fight back. If you want to send 5 years proof and that is not a pain to obtain, send that. But make sure you write a cover letter along with your evidence. Start by ...

Hello, Hope some one can provide me with an advice or an opinion on this. I applied for BC November 2015 via NCS and the lady who assist me advised me that the home office will request proof 5 year residency from my self at a later date because at the point of application I did not provide any. My ...