Mr. Satire wrote:

I'm not sure about all of the bosses, but I think the Bowser battle at the end (and any other boss that require scaling) is done with the SNES's sprite scaling abilites, which don't use Mode 7. Mode 7 can only be used on backgrounds, not sprites.

[SPOILER:6b82e17ce2]Mode 7 can only work on backgrounds, not sprites; therefore, any object that does not rotate/scale with the background must be a sprite, even items that would normally be thought of as part of the background, such as fixed platforms. The game developer must create a sprite with the same appearance as that object. For instance, in Super Castlevania IV, battles in which a boss rotates, such as with Koranot (which is a large golem), have the mobile boss as the background, while the blocks on which the protagonist stands are sprites. With the obvious enhancements, this is similar to how some NES games featured battles against a giant movable boss without the slowdown and flicker inherent in a large sprite set—by making the boss the background, and then moving and animating it. Both systems' examples only must apply to objects in the horizontal plane of the moving object. For instance, a floor, ceiling or scoreboard can remain part of a background in both the NES and SNES examples as long as they are completely "above" or "below" the field of gameplay. They can also be turned into sprites if the whole screen is needed, but this can cause slowdown.

That Mode 7 cannot be used on sprites means that each "size" of an "approaching" sprite for a given distance has to be pre-drawn, meaning that one would see sprites "jump" between a limited number of sizes when "approaching" them. This can be seen in Super Mario Kart and HyperZone whenever an object approaches, or when walking vertically on the Final Fantasy VI map with an airship in view.

Similarly, sprite "rotations" have to be handled through pre-drawing unless they are done with hardware included in the game cartridge such as the Super FX 2 chip as with Super Mario World 2: Yoshi's Island. A notable workaround does exist and can be seen in the second boss battle in Contra III: The Alien Wars and the battles against Reznor (platform wall support), Iggy (battle platform), Larry (also the platform), Morton, Ludwig, Roy, and Bowser in Super Mario World. In these examples, the boss is a "background" and therefore rotates through Mode 7, and the scoreboard, which is "above" the field of play, is also a background, but the floor of battle's cracks are, as with the players and gunfire, "sprites" that are redrawn under various rotations as the player rotates. However, this only allows one "sprite" to be manipulated at once.

One exception to Mode 7-like effects on sprites handled neither by pre-drawing nor by external chips occurs in Tales of Phantasia and Star Ocean, where re-rendering of sprites on the fly is done entirely by the software. In ToP, the player sprite vertically stretches upon walking onto a save spot, and in Star Ocean, items "squash" upon "popping out of" an open treasure chest. Due to the extra tiles needed for such rendering and the other high system demands throughout those games (both used a form of streaming audio to circumvent the SPC700's limited capacity, and as with most high-end SNES RPGs, used a variable width font), such rendering was limited to those few scenes.[/SPOILER:6b82e17ce2]
The short answer is you're wrong. The long answer is that you're technically correct, but programmers found ways around that limitation.