Hmmm… it’s also possible in that scenario that Hermione was hot-swapped out of the combat. Real!Hermione responded with a terrified scream to the Patronus, and while Present!Harry was racing to her on a broom, Time-Turned!Harry did some kind of obscuring spell (fog, blast of light, something like that), tossed an invisibility cloak (not Harry’s) over Real!Hermione, and then fed Simulacrum!Hermione to the troll just in time for Present!Harry to show up.
Hmmm… it’s also possible in that scenario that Hermione was hot-swapped out of the combat. Real!Hermione responded with a terrified scream to the Patronus, and while Present!Harry was racing to her on a broom, Time-Turned!Harry did some kind of obscuring spell (fog, blast of light, something like that), tossed an invisibility cloak (not Harry’s) over Real!Hermione, and then fed Simulacrum!Hermione to the troll just in time for Present!Harry to show up.