I think the idea is that across voters, the average difference in preference for A vs B is revealed by choice of voting strategy along the lines you're mentioni

I think the idea is that across voters, the average difference in preference for A vs B is revealed by choice of voting strategy along the lines you're mentioning. If your preference for A is strong enough that you want to secure a vote solely for A then that choice of strategy does so. But if you want to preserve votes for A and B both, you can do that. Presumably someone else would feel differently, and it would be reflected in expected voting patterns. No system is perfect, but at the same time, at some point "strategic voting" becomes revealed preference. The issue is how well a voting system encodes these things.