I have never ever in all my years of listening to headphones lowered the volume of the source before plugging in the headphones.
I have never met or know anyone who does this or suggested I do this.
If what your saying is actually true I myself and everyone I know must have been very lucky not to ever damage anything.
Slightly sceptical about this as the manuals would warn about doing this surely. Companies wouldn’t want there products having bad reputation.
Never experienced this either
I think this is what I may be experiencing.