Your comment is thoroughly unfair on a whole book full of insight and useful, actionable advice that can be applied profitably to competitive situations in business. You criticise one example, saying it does not fit your definition of strategy vs tactics (a topic the book doesn't even cover), and appear to discard the entire book based on that. This is a very unfair way to treat a book and I encourage you to think about what you write, when posting negative criticism of this sort.
Your comment is akin to implying that 2001 is a crappy movie because it doesn't fully explore the effects of void on the exposed human body. Yes, that's true, but it's entirely irrelevant.
For what it's worth, at the core of the Good/Bad Strategy book is a useful definition of strategy as a combination of three things:
1) An insightful diagnosis of the situation
2) A set of guidelines/policies/plans to take advantage of the diagnosis
3) Coherent action to implement that plan
In merely laying out and explaining this definition, this book enables the reader to correctly make the difference between useless fluff and actual strategy. Rumelt then explores all three stages and, in particular, spends a lot of time (rightly) on presenting tools that can assist in generating the insightful diagnosis (aka "aha moment") that is a prerequisite to good strategy.
Irrespective of whether it is "strategy" or "tactics", Nelson's key insightful diagnosis, according to the book, was that his seamen were more experienced at firing cannons in choppy waters than the more numerous Spanish/French Armada. Based on a "fair fight" situation, the British would have lost. But Nelson leveraged his insight into a plan that enabled him to pit the British fleet's strengths (skill at shooting in choppy waters) against the Spanish/French armada's weakness (lack of same skill), instead of pitting the British's weakness (numbers) vs the French/Spanish's strength (again numbers). That insight won the battle dramatically and set up the British Navy's domination of the seas for centuries.
Conversely, saying that Nelson's "strategy" was to have a decisive battle vs a skirmish is, by Rumelt's definition, a great example of "bad strategy". There's no insight in that - just a wish, a hope. In short, "Let's win with a decisive battle" is wishful thinking, in the same way that "Our strategy is to grow our usage numbers by 6% every week" or "Our strategy is to double our turnover next year" are wishful thinking.
Strategy begins with an insight of how to change a losing situation into a winning one, and follows with plans and actions to take advantage of that insight. Whether you then call it strategy, tactics, or some term of your choosing, is fairly irrelevant. The point is, this book presents, with great detail and tools, a solid way of thinking about strategy that can actually be useful to someone who actually needs to "be more strategic" and, as the OP appears to be, is confused about what that even means.
Sorry for the rant - I just felt irritated by the brief and unfair put-down of my heartfelt recommendation of this book in what I perceived as an unfair way.