Answer: false. A tippet is defined by where it sits and what it does, not by whether it was knotted on. It can be the terminal section of the leader — the fine end the fly is tied to — or a separate piece knotted onto the leader when that end has been cut back.

The practical difference is only how the leader is built. A knotless tapered leader ends in a tippet section already; when the fly has been changed a few times and that section is short, you knot on a new piece of tippet. A leader built from sections has a tippet section from the start, joined by a knot to the heavier line.

So add tippet when the terminal section is short, and do not describe the knot as the thing that makes it a tippet. You can also carry a spool of tippet and add it to any leader that needs a finer or longer end. The definition covers both arrangements.

Source

From the FFI knots and rigging terminology; terms follow the FFI Fly Casting Definitions.