Firstly, the headline numbers are fairly meaningless on branded torque wrenches, so i'd expect them to be even more meaningless on a Chinese eBay special.
However, for £33...and if you already have Makita batteries, it's hard to think of a reason not to give it a whirl, especially as you can get the same thing from Chinese selling sites for £25 inc del. As long as you don't expect it to be anything special, anything more it does is great.
I've got a Ryobi impact wrench and it's not the most powerful thing in the world, but in reality it shifts old suspension bolts just fine. I've taken off loads of 10-15 year old pinch bolts, suspension arm bolts, ball joint bolts etc and the overwhelming majority whizz off in less than 3-4 seconds. Maybe 5% of them take 10-20 seconds before they free off but they all eventually free off safely. I'd imagine it'll be the same with this sort of thing.
If nothing else, it's so much safer taking of things with an impact wrench than with giant breaker bars that are at high risk of shearing bolts. Also an impact wrench allows you to free off bolts which are at high risk of being rounded by handtools as it's hard to keep the socket square (old brake disc bolts!) and they're also great for bolts which requires a counter wrench (shock absorber top nuts, ARB links, ball joint bolts).