The 25x number already includes this effect. Methane is much much more potent than CO2, but since it breaks down rapidly then over the course of a 100 years the average effect is 25x.
So: if you first say "25x" then you cannot say "break down" afterwards because that is included in the 25x, you are then mentally including the breakdown twice.
There are also higher numbers in use than 25x that is used for the effect over shorter horizons. But 100 years seems like a good horizon for the humanity getting through the crisis or not.
