Whoever posted this is not a programmer. Does no conditional on that code so it would run on every browser on every session so where's the check for Firefox?
Unless they are claiming that it is injected at runtime. But that's easily provable/disprovable with agent spoofing.
In the demo I saw they did an agent spoofing to Chrome and the delay went away, but it didn’t look very extensively tested. As others said, the disappearance on reload could easily be because they thought he was returning to the page and had already seen the ad/been punished for not seeing the ad and so something ad-related disappeared instead.
Iirc the thing is it loads a different js file when it detects chrome which doesn't have the 5s delay. The reasoning is this is part of some anti adblocker code and chrome didn't need the extra logic.
The code is still present when spoofing the user agent or even using a freshly installed chrome. The demo video loafing faster after spoofing can be due to many different reasons.