*You post a random picture of a house* Someone: You bought a house! [duplicate]

From the Friends TV show:

Monica: I have some pretty exciting news.
Phoebe: You're pregnant!

Monica was in a relationship and had expressed that she wanted kids, but didn't have a tummy and hadn't given any hint whatsoever that she may be pregnant.

Is there a word to describe these guesses that may be technically feasible but that are very exaggerated?

It's somewhat like the domino effect meme

For example:

• You posted a picture of a house. Did you buy it?!
• Well that's a ____. No, I didn't, I just like taking pictures.

Solution 1:

How about jumping to conclusions?

Defined by Wikipedia as:

a psychological term referring to a communication obstacle where one "judge[s] or decide[s] something without having all the facts; to reach unwarranted conclusions"

With respect to the updated example sentence you could use

… that’s a [big] leap / that’s a [huge] jump … etc

Or you could remove the article:

… that’s jumping to conclusions

Solution 2:

The word you are looking for is presumption (noun), presume (verb). You could alternately use assumption (noun), assume (verb).

Quoting from Lexico

Presumption (noun)
An idea that is taken to be true on the basis of probability.

Quoting from Lexico

Assumption (noun)
A thing that is accepted as true or as certain to happen, without proof.

This is close to the idiom "jumping to conclusion".