He wasn't factually correct but he was kind of on the right track.
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AI Overview
Yes, smart TVs can collect data from devices connected via HDMI
using
Automatic Content Recognition (ACR), which identifies what you're watching (from consoles, Blu-ray, cable boxes) by analyzing screenshots, and sends it to the cloud for ad targeting, but this is usually opt-in via privacy settings and can often be disabled in the TV's menu. While the HDMI cable transmits picture/audio, the TV's internal software, not the cable itself, performs the tracking, often through its built-in Wi-Fi connection to the internet.
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So the key takeaway here is do not
EVER connect your tv to your home wi-fi. If you absolutely must connect to the internet for setup or to get updates do it through hard line ethernet then disconnect it when you are done.