Not really. Some are safe even you do like this:
I’m familiar with the tolerance for automotive stuff. It should be fine 99.999% of the time, but I also know someone who ended up with a dead ECU from a 24V jump. Mind you, it was a modified car with an aftermarket ECU, so who knows what they designed it to tolerate. OEM equipment should be fine.
Like I said, just not a risk I would personally take, and I won’t recommend it, but it would probably be fine. I also probably have more options than most, since I build my own stuff usually. I built my own jumper battery out of 4P4S A123 ANR26650M1-B cells. Now those things pack a punch, rated for 480A 10S pulse, and in reality they can do more.
That's a nice jump starter setup, not cheap but certainly quite good. It's output voltage can still be above 10V while delivering ≈280A, quite nice, and down to ≈8V for these 480A. Not cheap, of course.
I believe something could be gained via stepping up from 4S to 5S LiFePO4 setup. 
I believe the two (LFP and LCO) has its own advantages and disadvantages.
You could ask the CS to check if they are professional or not in Car Jump Starter industry.
In a pinch you can use a power tool pack as long as it’s got enough cells to sag and still push the load(14-18v nominal with Xs 2p).
You mean you do not suggest use it?
4S10P HB6s charged to only 3.92V/cell to ensure maximum cycle life, starter total useable capacity would still be ≈10Ah. 
Well, peeking at the pulse discharge graph I believe a (4S) 6 to 8P setup would still shake up pretty nicely most weak starter battery ill engines. Nice 50 and 60A pulses! 
which one do you sell,
can we have a discount code please?
Tattu Jump Starter is made from LiFePo4 Battery. PM to me if you want to know more.
Yes. This is right.
It seems you are just here to promote “Gens Ace Tattu”
Marked as Spam.