Depends on the movement (and your goals obviously). Holding a bench press at full extension is putting all that stress on your bones and joints and practically none on the intended target muscles (see “deloading muscles”)… certainly less than ideal for hypertrophy.
Seems like a hold at the top of the deadlift would be as effective building your dead as a hold at the lockout of your bench would build your bench or a hold at the after the unrack would build your squat.
In other words, I doubt it’s terribly beneficial for those lifts. But a pause on the chest or a just above the chest like with a Spoto press I’ve found to be hugely beneficial. Same with 3-5 second holds in the hole with squats.
I like to hold it gently. Like holding a sleeping baby you dont want to wake. Sometimes, I caress the iron I’m using so it knows it’s not personal when I spank it.
Lastly, when I am in the mood, I like to dry hump the machine I am using. This allows me to spread my scent on it so when others use it they know I own it.