Couldn't that be said of most, if not all religions, ie, you don't have to be a Christian to follow a "Christian" way of life*, similarly, you don't have to be a Muslim to follow a "Muslim" way of life*, if you so wish. To mention just two of the worlds many religions.
*Whatever those may be.
Nope, to be 'properly religious' you have to have faith in unseeable unprovable entities such as God.
In the case of Christianity, you should believe Jesus was the 'actual' son of God.
And you should believe in the existence of such a things as a soul or spirit that is in some way separate to the human body.
Buddhists don't 'have' to believe in any of that supernatural stuff.
(Although believing those things doesn't preclude you from being a Buddhist)
You can follow the philosophy / teachings / principals of Buddha without any 'religious' or supernatural belief, and still be A Buddhist.
If you decide you like the general morality of a religion such as Christianity, and try to follow that, but don't actually have faith or believe any of the supernatural entities then you're taking moral advice or guidance from say Christianity - but no, you're not actually Christian* if you don't pursue the faith / belief bit.
*Even if it turns out you're actually a *nicer* person than those who claim Christianity for themselves, but who themselves turn out to be rather unpleasant.
Tl;dr
No.
