Aye - it may be generic but it disnae puff - ergo, incorrect. It may sound pedantic, but would you refer to every fishing vessel as a trawler?
If you are going to be pedantic then the term 'Puffer' can only be applied to the original scows fitted with single-cylinder, non-condensing engines that exhausted directly to atmosphere and thus created a puffing sound. As soon as the compounded, condensing engine came into use, the puffing sound was eliminated. Nevertheless, the small coastal craft plying their trade on the West Coast continued to be known as 'Puffers'. VICS were added under this heading when they came into service in the coastal trade. Even when some of them were converted to diesel they were still know as puffers and even those in the last days of the trade that were laid down as motorships were still known as Puffers. It was a specific term that became generic through long usage and familiarity. Consider the analogy of the 'hoover' as a generic term although many vacuum cleaners are made by manufacturers other than Hoover.
If you are to insist that only the original single-cylinder, non-condensing engined craft should be known as Puffers, what would you have all their successors called?
Finally, no I wouldn't call every fishing boat a trawler but then their roles are far more specific while a puffer would carry any cargo and adopt any role that paid the owner.
Barry M