Did you try reloading the phpinfo page? It might be using one stored in the cache (especially since other generated pages are displaying the correct version).
Also, maybe they just forgot to change the phpinfo function's output in 4.3.3, for whatever reason. I really don't know.
When you installed 4.3.0, did you compile it into Apache, compile it as a DSO, or as a standalone binary? If it was one of the latter two, did you install 4.3.3 to the same location as 4.3.0?