In that example, I'm pretty sure that the 'require' line is compiled to opcodes, but not executed, until that line is reached. Supporting evidence: https://stackoverflow.com/questions/37880749/when-is-a-php-i...

So if there's a 10 second gap between the start of execution and the 'require' line being reached and evaluated, then any incompatible changes to the file being required within that 10 seconds will cause an error.