Superficial surface finish cracks are prone to all guitars. Importantly, more in used guitars.
Strats tend to crack the paint or finish surface in that exact same spot where the neck meets the body. Used guitars are especially more prone as they have been handled more.
If you bought a guitars that was not listed as Mint, NEW or Perfect
then it’s a used guitar. Ordinary wear and tear and surface cracks are to be expected sometimes, so clearly a surface crack in the body where the neck meets the pocket is a non-issue. Equally important, if a used guitar plays well and sounds good and is in excellent playing condition
why worry?

The “Real Value” of used guitars

Remember-most used guitars aren’t beauty pageant entries, just good possibilities as great playing guitars for you.
You need to ask yourself? Did I buy this guitar to play it or look at it?
When you said nothing about how well it plays but just how it looks it’s not the guitar with a problem.
The real value of a “used guitar” is that it allows a player to have some experience with a higher end instrument without the higher cost.
I really hope as a serious player you try it to determine if it plays excellently.
Most guitar players are Divas, sure I get it. They are superficial and tend to choose instruments as they would a girl friend.
Don’t do that. It’s a tool. If you buy a dull tool-then don’t complain…sharpen it!
image Haywire Custom Guitars neck and body fit on a used guitar.Haywire Custom Guitars neck and profile + back contours for ease of playing.
To an untrained eye-sometimes what may look like an issue is usually not an issue at all.
When paint is stripped from a used guitar body there will be a space where the excessive amounts of paint used to be.
As a guitar builder-I want some space for my guitar necks to align properly. That is a very important part of setup later on.

Not every neck fits perfectly tight

When adding a neck to a guitar body there are 4 axis which need to be perfectly positioned. As follows: right, left
and forward and backward neck alignment. If the neck is perfectly aligned on all of those axis-it will play properly.
When buying a used or new guitar that is what to look for.
Look at the margin space on each side between the neck and strings.
Ideally you should see the same amount of neck space from each of the “E” strings to the side of the neck-all the way down.
That will give an indication of the proper alignment to right and left axis. Further, the strings will ride just over top of each pole piece on each pickup. That is another indication alignment is correct.
Not every guitar neck fits perfectly tight with every body. It doesn’t need to.
It just needs to align and play well.