That sounds like you might have to refund some or all of your contributors. After the acquisition, your project will cease to exist. It's unlikely that both crowdfunding promises were exactly the same. Even if the intention is to fold your product into theirs, the realistic outcome is that your employers will ship the product as they intended, leaving your supporters with little to nothing. You need to clean this up now, rather than later.

I wouldn't call it "bootstrapped", then.

For me, a company is bootstrapped if it makes enough money from its products to sustain itself and its founders/employees.

"We've bootstrapped the company so far, but we don't think we will ship a MVP without taking at least a seed round" wouldn't draw any protests of misuse, in my experience.

You are correct that most bootstrapped companies that have launched end up supporting themselves; that's survivor bias in action.

Then when you go back to talk to these folks, give them the rationale and the small numbers rather than (just) the big number. If they have issues with your methodology you can likely work it out.

This is largely covered by the book, "Getting to Yes". Short and helpful.