While Tom is basically right, he's not technically right.
There is a separate digitizer for the iPhone 6s. However, its bonded onto the LCD. You can peel it off if you try hard enough. However, the problem is getting a new digitizer on the LCD. The digi is bonded onto the LCD. It is possible that you could use some sort of heat stamping method to get the new digi on, but you have no way of getting it lined up. The process used to line up and bond the digi to the LCD involves a machine that uses x-rays and sometimes lasers to line everything up down to the fraction of a mm. It then bonds it in a special process.
So the quick answer is yes, you could save yourself the extra $30 that a screen with a digi attached would cost. But it would cost about $5,000 in machinery and I don't know how long in time to acquire the skill to get things right.