Not necessarily. (1) Landing pages are relatively simple to fake; just because the link goes to Google, it doesn't mean that Google has authorized an account on Amazon to sell the products. (2) Amazon has been known to mix stock, so even if the seller actually is Google, you might end up getting a product from another seller, which might not be authentic.

Personally, the last 3-4 phones I bought off of Amazon were all different models from what they had been advertised as. It's possible that you might get lucky and receive an authentic phone for less than buying from Google directly, but if you actually want confidence that you will receive the real thing, get it directly from the manufacturer.