If interest rates were, say, 8% I would agree it would be unreasonable to plan for a 75% increase. I know. I had a mortgage when rates increased 5% in a day.
However, when base rates are 1% it is not unreasonable. Think of it as points increase. To plan for a 3% rise in base rates should always be in people's plans. It certainly has always been in mine and the lenders I have borrowed from.
To me it's sensible planning for the future. Something I have always done. Perhaps that's one of the reasons I was fully paid up and mortgage free by the time I was 53.