It can be clearly seen from the code that reading past array boundaries WILL occur in compiled code:
And yet, on 22nd April 2023, you said:
This is not issue of my code, because if I do not declare "topline" array, then "botline" reading works fine.
Clearly putting blame on anything BUT your code, be it the PIC itself, the compiler, the assembler or whatever - just not your code.

But, you're right, some situations could be confidently detected and some could be flagged as "potential" at compile time but it's a "can of worms".

As it is, the rules are clear and they are spelled out in the manual, section 7.6 that Ioannis pointed to earlier. You are responsibly, a fair price to pay for a powerful feature. It is what it is.