#2 The line was scripted and WWE regretted their decision instantly
Okay, so AEW have taken shots at WWE on May 25th, and the Double or Nothing pay-per-view was received to great critical acclaim, so it's only to be expected that WWE were aware of this and wanted to react in some way directly.
Of course they knew they would shock the wrestling world with a mere mention of AEW. No real shots fired, nothing too controversial - but guaranteed to make headlines within the context of their past record of completely ignoring any other wrestling promotion...
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Script Sami Zayn to mention AEW, and it breaks the internet. But say, a few hours later, or even a few moments later, officials think they've made a mistake. Maybe it wasn't so well received, maybe the 'AEW' chants took the shine away from WWE.
There's every chance that WWE opted just to simply remove the chants and return to their norm of not having a rival mentioned in WWE at all.