Why sceptical? Yes the measures on the one you have are the same as the proper one...no doubt about that.
BUT...the one you have will stop when it hits the bottom of the sump...the proper one will stop above the bottom of the sump because it is designed with a wider bit that hits a stop (see pic, again, in post 12).
It's not rocket science. The only way you will be convinced is if you use both and compare the results. You will have to do this for yourself however. Post 18 in the thread I referred to earlier has, however, done it for you. It's up to you...don't shoot the messenger.