The technology is unlikely to improve meaningfully in 7 years. And you'd only upgrade if it was a financial improvement so it makes complete sense to give an estimate based on keeping it for 20 years.

I don't see what your issue is.

Then you are unlikely to be the person I'd be taking advice from.

Let me rephrase: the thing that you said clearly isn't an issue so it doesn't make sense for you to have an issue with their advice.