those are fair points. I'm not going to die in a ditch over it. I do agree that having multiple titles at a tournament is a good defence against the argument of opportunism (and btw I don't think there's anything wrong with opportunism, stone cold killas should be doing that)
To be clear, I DO think Nadal is opportunistic, both within a match and in his career in general. I just don't think the main take away of his inability to defend a title outside of clay should be opportunism, that's all.
In general, I think Nadal's won outside of clay a lot in his best seasons, while he struggled to do so in other seasons, whether it was due to form, injuries, or an opponent who had his number. It's more or less that simple.
For example, in his first big season outside of clay, 2008, he won: Queens, Wimbledon, Canada Masters and the Olympics. That's pretty huge.
In 2009, he won the Australian Open and Indian Wells, before injury prevented him from attempting to defend his Wimbledon title.
In 2010, he won Wimbledon and the US Open. I mean, those are 3 consecutive seasons in which he's had a very good to outright stellar resume outside of clay.
In 2011, his main problem was Novak, who beat him in the IW, Miami, Wimbledon and US Open finals.
Injury cut his season short following Wimbledon in 2012, but that was a season in which he struggled outside of clay, despite coming very close in the AO final.
In 2013, he had an absolutely incredible year on hards, going undefeated until September on the surface (though in fairness, he didn't play the AO Open). He won Indian Wells, Canada Masters, Cinci Masters and the US Open.
In 2014, following his injury and loss in the AO final, he again struggled outside of clay before skipping the rest of the season after Wimbledon (maybe he played an event after that but I can't remember honestly).
In 2015 and 2016, he didn't win much of anything, on any surface and was clearly struggling with overall.
In 2017, he won the US Open, which, despite playing very well, I would actually qualify as opportunistic, as he capitalized on a very good draw, Roger being out, and the absence of some very important rivals.
Anyway, the reason for the "history lesson" so to speak, is that it tells the story more or less accurately. That's too bulky of a resume outside of clay to be qualified as opportunistic, even though I don't take umbrage with the term itself and I agree with you, it's not a negative thing at all.