IIUC, the first setup couldn't be exploited because the site didn't run any php. You kinda need the server to run some php if you're gonna use a php vuln. It got solved ~2h after they added a php-version.php ...

FTA:

> The failed leaks highlight a broader challenge: building a generalized exploit that works reliably across PHP versions and deployment configurations is difficult. The kit’s B1 layout was calculated for the official php:8.4.26-apache image with a 128 MB memory limit. Other instances like our Roundcube honeypot ran the same PHP version from a different build, with additional extensions and a 64 MB memory limit. These differences can affect heap layout and memory reuse, potentially preventing the leak from working as expected.

It sounds like it's hard to put together a generalized write-once-run-everywhere version of the exploit, so you need a human or an expensive LLM backing each attack and trying to adjust for the particulars of that target's deployment.