Au contraire - this is since its RID(2015) technically an Aligned-Universe Grimlock so he is supposed to be pretty much the same as Grimlock appeared in Fall of Cybertron since according to Hasbro its all the same universe and continuity (WFC/FOC/Prime/RescueBots/RID/The Covenant of Primus etc) ergo the same character. And FOC Grimlock in style, look and colour scheme was heavily based on the G1 version.
I do take your point though - and hey - I bought him didn't I?
I've often wondered if you count the old Excavator Grimlock from the original RID as a 'Grimlock Grimlock' if you catch my drift, or it was just random use of the name? I'm setting up a Big Grim display in my shed and not sure whether to include him or not.
If you have a look in the January Jubilations thread (in the post just above yours) there is a pic of him next to the new deluxe sized Aerielbots - you can see he's at least a good head shorter than Firefly whom he is next to.