You're using your own definition for a linear progression there - the context for my comments has been "a series of three civs that is equivalent to 1 old style civs split into 3 ages". Noone wanting to play England for the entire game would be satisfied with a Roman starting point for that. Rome would have it's own linear progressions through some renaissance Italian state into the Italian Kingdom or something.
The Rome - Norman - Britain was an example the used of an unstacked / non-linear civ that showed how you can make it work by looking at different civilizations and their impact on the development of the city of London.
Goths - HRE - Prussia is explicitly seen as a "German" stack / linear progression by OP and many in this thread and other dlc prediction threads. It would be odd if we suddenly got a full stack like that on the first DLC pack imo, as that has expressly not always been the design. That may be the end point, but suddenly changing to prioritising another stack all in one go would be at odds with their philosophy for choosing civs thus far, barring China and India for the reasons I've set our earlier.
I don't think that's controversial, it's been the main talking point on these forums since we saw that first diagram showing Egypt into Songhai. Civs are no longer stacked. Releasing a whole stack in one go would clearly be a change of policy.
I think every player will have their own idea of what a “linear progression” is.
Certainly I consider Roman – Norman – British a perfectly reasonable progression. All are cultures that ruled England, and while not complete, it is entirely congruent with the way history is taught here.
I would suggest also that your (apparently far more universal!) concept of the Goths to Prussia as a cromulent German “stack” is a little off, given that the only evidence we have of Gothic representation so far is the Mausoleum of Theodoric. Theodoric’s Ostrogoths migrated from east of the Dniester into Italy, and so would appear to have very little to do with the Kingdom of Prussia. Even their relationship to the (Frankish) HRE would be one of (slightly) overlapping territory.