There are 6 songs that I've GSed (Xguitar) for which my score still isn't in the top 20% of logged scores. 2 I've FCd on expert and am still outside the top 20%. There's definitely a lot of credence to "The players that are playing now include a monumentally far greater proportion of top-level-expert players than before".
I can confirm this as well. I specifically remember chuckling after an Expert FC that I thought used overdrive pretty well and still not even being in the top 10 or 15%.