For years, we've been making pasta sauce that incorporates extra firm tofu. To prepare the tofu for crumbling we follow this procedure:   cut tofu into pieces cover with water bring to boil drain mash with potato masher squeeze out water by wrapping in towel and twisting add to tomato sauce   How does boiling affect the change in the texture of the tofu? 
Boiling tofu causes the bean curd to exude moisture, so you are correct there is a structural difference between boiled and unboiled tofu. The heat tightens up the protein structure, hence affecting consistency. Boiling bean curd for braised and fried dishes is a long practised technique in Asia, partly for these reasons. Because of the structural change, boiled tofu can stand up better to more vigorous cooking methods like long simmering and frying.  The type of tofu (mainly its coagulating agents) are related to the efficacy of this method, but it absolutely applies to your typical firm supermarket brands (non-silken). 