That's not true because most of he poor's income goes on food and heating fuel which are not affected at all.
The wealthiest will benefit proportionaly more as they spend more on luxury items.
Thus the cut will not stimulate the economy at all.
What would help is a 2.5% increase in benefits.
But he won't do that because he would rather cut his own throat than help the least well off.
Be prepared for a mega-depression.