Yes - it certainly does seem that way. Michael Brookes mentioned recently that powers have an additional central cost based on their size - which is certainly needed as a centrally-located power like Hudson or Winters still has marginally profitable systems close to the edge of human space - but it doesn't seem large enough to be a major limiting factor on the big powers at the moment: still plenty of opportunity to expand and do so much quicker than the small powers can manage. (The overhead must end up being quite significant eventually, because the distance-based cost increases linearly but the number of systems available at a particular distance increases cubically so long as you don't get too close to the frontier)
The way the mechanics are set up I think makes it a very bad idea for Frontier to do anything further to assist intra-power coordination (or indeed prevent double-agent sabotage) despite how obviously popular such things would be with players.
The mechanisms of PowerPlay are all fairly straightforward ones (it's been described as a "board game" and indeed all the mechanics are - barely - within the level of complexity that you could play it without a computer) which means that the "right" decisions are generally fairly obvious: fortify all your control systems, prepare a few good candidates for expansion up to your weekly budget, make sure last week's prepared systems are expanded and oppose and undermine as many opposing systems as you have time for.
A hypothetical power with perfect central control - which would be easy enough to achieve in-game by letting a basic power AI select preparation targets, and stopping (or seriously tapering) merit awards for actions which aren't useful - fortifying or undermining systems already at their thresholds, preparing systems other than the target ones or preparing a target system significantly beyond the level of opposition from other powers, etc. - would become incredibly efficient compared with now. At that point the bigger initial powers have a massive advantage. With the ability to prepare ten systems, which the top powers have, ideal play would allow an increase in CC surplus by around 500-1,000 a week, which would rapidly get out of hand: they already have enough CC to prepare whatever they like, more or less ...
Once - if! - you get to the point where overheads are becoming too high, then it's probably optimal to intentionally prepare no systems at all, or if you're in the bottom three despite being ridiculously large, prepare just one, and go all-out for ensuring expansion into it succeeds. At some point you might end up with too many systems to fortify them all ... but at that point you probably have too many systems for your opponents to undermine them all either, so you can afford to be a bit selective with "ideal" play.
(That's the "peaceful expansion" strategy - once you have a few thousand CC surplus to play with, though, ideal play would let you go for a much more aggressive strategy of setting up control systems 15.1 LY (or thereabouts) from opposing control systems of small powers - you can afford to expand somewhere loss-making or barely profitable; they can't afford to have a significant fraction of their exploited systems switch to contested)
I don't know whether the incompetence, incoherence, perverse incentives, and occasional active sabotage which means all powers are doing far from optimal stuff is intended by Frontier or not - but it does seem at this stage to be required to avoid the larger powers expanding extremely rapidly, and the smaller powers from being too easily flattened.
