Exactly! You only have so much energy to give on the day, if you're using a good bit of that energy on the swim due to lack of training/conditioning then it's energy lost that could have been used on the bike/run.

Even take that a step further, and you could argue that every 10 watts of energy spent at a 85-90% intensity, will cost you maybe 12 watts at 75-85% intensity due to how different energy sources are utilized and muscle fatigue.

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Is a swimmer going 38min by definition less efficient than one going 26min? Doesn't it have more to do with how much effort they are extending? They may be slower, and there are clearly issues with their stroke, but that doesn't mean that they are necessarily expending more energy than the 26min guy. I would think that once well-conditioned, the only thing that matters in terms of how many matches are burned is not your speed, but rather how close your swim speed matches your threshold pace.