There seem to be a few TRE's out there that like to throw that one in.
Everyone I know has always continued to land after declaring a mayday if they had time before landing.
And they have always taken great pleasure afterwards in debriefing that they did it wrong even when the fire bell went at 200ft.
Seems daft to me because they want TOGA power on both until you reach acceleration alt which is just potentially chucking more fuel on the fire in my book and getting all the gasses in the hot section hotter. So if it was just a gas leak on my type you have just tripled the amount of gas going through and got the egt up from 320 up to 640 degs.
Mind you I have had a injector pipe come off spraying fuel all over the hot section and it never caught thankfully. Just a drop in torque/egt in flight when it happened and loads of white smoke coming out of every hole in the cowls when we shut down on the ground.