对于PHP脚本，I / O使用限制是否可能导致服务器超时？

I am having a very strange Server Timeout error (Error 500) for a process (initiated in a PHP script) that hits the I/O Usage limit of 1MB set by the hosting provider.

Is it possible that this I/O limit actually causes the Timeout error?

Before you ask those are the PHP values I test with:

max_execution_time 0
max_input_time -1 

If not the I/O limit, is there any other server limit that can produce a timeout error?

Usage screenshot