TTF tells the Win32 subsystem to trigger an update of all UI elements on the screen; specifically assigning tooltips the highest z-index to ensure they're on top.
Off the top of my head, TTF itself doesn't actually reserve any memory (though I'd have to check to be 100% certain), most likely any memory-related issues experienced with TTF are due to Win32 function taking up tons of memory (not in our hands) or with - as you mentioned - lazy GC behavior.
But I'll double-check just to be on the safe side
