If you have no idea how to build that product, no plans, no realistic way to do it, then yes, a deception.

If you have a proof of concept, have put in some thinking, made UI sketches and flows, etc, you have started building the product, because you can't advance further without that. But you have to find out if it's worth putting more effort and money into it.

If the building of the product is contingent on the CTR, and the landing page does not mention that contingency but just says it’s being built, it is deception plain and simple.

Cleverly worded gotcha deception, sure. But deception none the less.

> If you have a proof of concept, have put in some thinking, made UI sketches and flows, etc, you have started building the product,

I think that that bar is too low to move from "we're considering building $FOO" to "we're building $FOO".

I mean, with the bar for "we're building $FOO" being "Investigate demand for $FOO", then the phrase "we're building $FOO" loses all meaning.

It's the difference between "we're getting divorced" vs "we're considering divorce".

"we're starting a new job" vs "we're looking for a new job"

"we're building a LEGO deathstar" vs "we're buying a box of LEGO"

I see no reason that "we're determining whether to build $FOO" is the same as "we're building $FOO"