Nonsense. It’s a simple continuation of something that has always been around. They would have needed to actively and purposefully changed it. The first company that tried to sell “1 Megabyte/s” instead of “8 Megabits/s” is shooting themselves in the foot because the number is smaller. If it was going to change, you would need everyone to agree at once to correct the numbers the same way.
Modems were 300 baud, then 1200 baud, then 56.6k baud. ISDN took things to 128k baud, and a T1 was 1.544M baud. Except that sometime around the time things went into tens of k, we started saying “bits” instead of “baud”. In any case, it simply continued with the first DSL and cable modems being around 1 to 10 Mbits. You had to be able to compare it fairly to what came before, and the easiest way to do that is to keep doing what they’ve been doing.
Ethernet continues to be sold in the same system of measurement, for the same reasons.