As a counterpoint, I got into the QF F lounge *as a non-QF flyer / -OWE* at SIN on a recent Friday, around ~4pm for an evening MH flight in J, but with AAdvantage Pro.

The lounge was starting to feel full by the time I left around 6pm at the front seating area, though the second section of the dining area still seemed to have place available.

[EDIT] Sorry, this was meant to be a post regarding non-QF flyers while being non-QF OWEs being able to still get into the QF F lounge @ SIN, but I forgot to include that detail!