Gideon would have been about to rotate. He rotates in more than 7 months.
GIdeon doesn't rotate until whatever the hell the Fall Block is.
you forget that WotC thinks in WotC Time™ which is to say Future Future League Time™.
What you perceive as "Gideon being too long in standard" to them is "Oh he's about to rotate, right?"
Hence the reasoning.
Also the fact of "There's gotta be a Gideon in Standard, else the Gatewatch isn't complete!" Reasoning.