

Might be. It is definitely a thing, though.
When I used to work for a large American corporation that sold products to consumers, they took it extremely seriously and breaking it would result in disciplinary action. It probably had something to do with advertisement laws, but it also easily could have just been because it makes the company look very bad.
one place even asked people to write fake reviews on Trustpilot/job sites
That sounds unethical, to say the least. Did they verify if you actually did it, or just “suggest” you do?
The magic cable typically goes into ISP-owned hardware sitting in a box somewhere down the street. From there, it’s either converted into fiber optic signals or repeated until it reaches an ISP-owned building where the data can be exchanged with the wider internet.
It uses multiple channels (frequency ranges) in parallel, bonding (combining) them to increase throughput.
A surprising amount of bandwidth can be achieved this way. DOCSIS 4.0 can do 10 gigabits per second in download and 6 gigabits per second in upload.