Its not a myth, but unlikely a non deflated tye will pop. I drop mine half pressure to keep bead in place-using tubeless
advice from CUK:
My bold..
Deflating tyres
This is not really necessary with bicycle tyres, since the maximum possible reduction in external pressure (about 10psi) has the same effect as that much extra
inside the tyre at ground level. Bicycle tyres are designed to stand way more than that. And even if one should blow off, it won’t contain enough air to damage anything apart from its own inner-tube.
In fact: leaving the tyres inflated helps to protect both tyre and rim from damage when the bike is handled.
Some airlines (e.g. BA) have realised this and exempted pedal cycle tyres from the usual restriction on the carriage of pressurised gases. Check-in staff prefer nice simple rules however, with together with a dose of corporate amnesia means that you’ll often be asked “have you deflated the tyres” even when flying BA.
Always say “I have deflated the tyres”. No need to say when or how much. One advantage of the packing rule is they cannot easily check – but if you argue they will. You’ll have deflated the tyres last time you had a puncture, won’t you, but it doesn’t do any harm to let a little air out when you’re packing the bike. 10psi is plenty.
The reason they have a rule about this is the amount of energy stored in a big tractor tyre, if it blew, could send the wheel through the side of the plane! And tractor tyres work at such low pressure, an extra 10psi might really make it happen.