Would a lower ranked player be allowed as much time between serving points as Nadal and Djokovic often take; I am not sure they would. .
you can be sure they wouldn't : I remember an article where many players were questioned on that and it was obvious for them : there's a "special allowance" for Nadal on that case, but they
can be sanctioned anyway.
I still remember when Cilic got a warning for time wasting just before a second serve against Fed on breakpoint against him in the US Open. And he had not taken so much time !
And in such cases, of course, players other than the top-4 tend to happen to think that they're not ruled the same as the others for every decision, not just time-wasting. It's just a natural process, that's why Tsonga is not the only one thinking that