Is pink ward v 6th item an intentional tradeoff decision?

Just curious if this is an intentional balance decision - I can see it being argued that, late game, having appropriate vision is tantamount to a 6th item, but this seems like a pretty steep tradeoff to me.

I know i'm not the first person to suggest some slot for pink wards - for example, as a late game upgrade to boots (which otherwise never have an active) or as a dedicated slot below trinket. I've just never heard whether or not there is a balance reason why this isnt the case.