The short explanation
The categories map to bandwidth: High Speed for 10.2Gbps, Premium High Speed for 18Gbps (600MHz), Ultra High Speed for 48Gbps (1500MHz). Certification means a testing program verified the cable, usually with a label that can be checked.
“8K” printed on a package means nothing on its own.
Where you run into it
At 48Gbps, cable quality stops being a detail. A marginal cable does not fail cleanly — it works at lower bandwidth and drops out at higher, or sparkles during demanding scenes, or fails only after warming up. All of which looks like a device fault.
Length compounds it. A cable that is fine at two meters may not be at ten, and active or optical cables bring their own direction and power requirements.
How the DR HDMI 8K handles it
The DR HDMI 8K's manual asks for a certified or tested 1500MHz 8K cable, copper or fiber, for a full 48Gbps link. The unit gives you a way to prove a cable is the problem rather than guessing: cap the advertised FRL rate, and if the fault disappears at a lower rate the cable is your answer.
Want to test your own HDMI chain?
The DR HDMI 8K is sold through the HDFury.eu web shop.