Technically, I suppose that is true but as neither appliance can create an overload I would not be concerned.does 26A vs (probably) 20A not represent a bit of an electrical difference?
I am surprised the igniter is said to require a 13A fuse - 3A would be adequate - a 13A flex being supplied and the reason, I presume.
Although, considering the demand for a NICEIC installer, perhaps the other instructions are not best thought out
Were it not a DIY forum, I would propose a different connection method.