You've got to go into this with your eyes open.
It's unlikely that a plastic boiler will suddenly catastrophically fail and instantly dump 5 gallons of boiling wort on your feet/floor/child/cat.
A typical failure will be the development of a small leak around the tap mounting or other similar hole.
Maybe a worse scenario is that you are fiddling with the tap when it pulls through the softened walls and causes a "wort spout".
Not good but nowhere near as bad as it could be.
So the message is you need to be sensible with the placement of the boiler and always be thinking "what if?".
If there are kids around then teach them the dangers and make sure they believe them.
If you leave the boiler boiling without any supervision (and I don't!) then make sure no-one else is near it.
In other words, acknowledge that DIY boilers are inherently a bit dangerous and use your common sense.
Hop and Grape have, quite rightly, decided to advise against using the new buckets as boilers because they have too little safety margin for them to risk a lawsuit in the event that something goes wrong.
I was never particularly happy even with a "proper" bruheat boiler. Even that would get noticably softer as the boil progressed so for me the solution was an ali stock pot and a gas burner. Still not risk-free but a whole lot safer imho.
That does not mean you should not use the H&G buckets as boilers. It just means you need to be aware of the risks.
Edit: I've just re-read this and realised I sound a bit like my dad. Which is mostly a bad thing....