Time dilation and black hole formation: Can they ever exist from an external observers' perspective?

[void4]

https://physics.stackexchange.com/questions/5031/can-black-holes-form-in-a-finite-amount-of-time

https://physics.stackexchange.com/questions/21319/how-can-anything-ever-fall-into-a-black-hole-as-seen-from-an-outside-observer

[...] this red-shifting towards undetectability happens very quickly. [...] the black-hole-with-an-essentially-undetectable-object-just-outside-its-event-horizon is a very good approximation to a black hole of a slightly larger mass.

It's important to differentiate between objects falling into a black hole and black hole formation itself.

A few answers I've found state that while black holes (except for primordial) never form from an external observers perspective, not only are the mathematical models good approximations, but the signals that we can receive redshift in a finite amount of time out of sight before the change "slows down", making them indistinguishable.

https://physics.stackexchange.com/questions/332456/can-you-have-a-giraffe-shaped-black-hole

tl;dr: Even from a distant observers' perspective, the infalling object travels the distance from several Schwarzschild-radii to very close to the horizon itself within fractions of a millisecond, where redshift etc. apply, making it practically indistinguishable from the black hole.

Edit: created this simulation using the equation from the answer: https://www.youtube.com/watch?v=0CwnWDjLh1c

What about gravitational waves detected from black hole mergers? What effect does this have on the signal?