Other teams cover their own ass, no one is going to go out and say "lol, did you see how bad they sucked... hahahahah", then be beaten 2 months later by that team.
The car barely ran fast so I doubt anyone was at all sincere when they said such things, it's a case of RBR being champions, you don't bad mouth the big boys no matter how badly they are doing.
Sunama has not specifically said they were terrible, but he keeps banging on about how everyone needs a 150point gap, which really would only be an issue if a team would be terrible in the first half of a season and turn it around completely. He keeps pushing the idea and implying that RBR weren't competitive at all until the half way mark in the season, which is pure rubbish. Likewise the tyres made little to no difference. The reason Red Bull improved comparatively was everyone else gave up on the 2013 cars when they hadn't.
There was nothing in running that suggested the car looked great, there was lots of "it looks beautiful, so it's probably fast" from people, but the laps they did were mostly very slow. Their fastest laps were miles off the pace, and they were often cruising around at 1:44's while others were doing 1:40's. The renault engine itself was spluttering around the track sounding like a dog on most of the cars. A car going slower is going to look smoother, but it simply couldn't have looked fast because it never ran fast at all.
I'm not saying they will or won't be good at some point this season, just that the apparent unbeatable in season development is down to very specific reasons like, them being the only team even trying last year. They were also the fastest team across 2012, Mclaren had a decent car but I think it was more a case of Mclaren not developing their car than Red Bull being epic in doing theirs. We know Mclaren had the biggest changes of anyone in 2013 and that meant starting work on it earlier, it backfired spectacularly both in ruining their 2012 season, being entirely the wrong choice for the 2013 season and probably pushing Hamilton out the door.
RBR were on par with Mclaren for the first half and moved significantly ahead in the second half, but Ferrari and Lotus improved relative to Mclaren as well.
I would say personally, at this stage nothing led me to believe it was uber fast if it was running well, it wasn't and isn't running well, once they likely open up the car a lot for cooling like every single other car on the grid has done will their aero remotely work or be completely broken anyway? On top of that Renault still seem to have issues, we have no idea how fast the engine is when it's running at it's peak(it could blow the other two away or be terrible in comparison) and the idea that Red bull can out develop everyone is fantasy as in both situations they've apparently done this there have been very good reasons. That's before you recognise that Merc have been building up for this season and weren't at full staff strength up till recently so you can't compare the "old" weakened team to what they can do and what they will commit to this season. Mclaren have had massive changes behind the scenes, maybe to late, maybe not. But this is the one season I can't see anyone not learning everything they can, we're at the start of a new reg's period meaning everyone will be developing hard throughout the next 2-3 seasons. No giving up half way through to focus on massive changes the coming year, etc.
It should also be remembered that with the opened up Ferrari, Williams and Merc cars, designed for hotter races, they also had over heating problems. The only Renault car that didn't was Caterham... which was pretty much designed to be the best cooled car on the grid. If Merc and basically every team with vastly more cooling than RBR are having overheating problems and RBR with much less cooling are having the worst overheating problems, I can't believe RBR can really do anything but open up the back, change the sidepods and improve cooling drastically. In doing so the car they've spent probably 18 months designing for the aero to work with a stupidly closed back end and tiny sidepods, will somewhat be wasted.
I think they'll turn up at Melbourne, or maybe even later, with a vastly opened up car and have to start aero almost from scratch.