It appears I either misunderstood or misremembered what I read.
It probably referred to MAC addresses being reused on WiFi. However the frames used are not Ethernet frames.
Ethernet however is not restricted to twisted pair cat cables it’s on fiber and originally was on co-axial.
When you use a hotspot from your phone the site/peers/whatever sees an IP that your ISP has assigned to you and could share that with authorities etc.
When you use a WiFi they see an IP assigned to the owner of the WiFi.
Security wise its easier for others in the WiFi to try and fuck with your computer since you are on the same LAN.
So it depends on what you fear the most.