Hi zexpress,
As you mentioned they call it a “medium feel” on their website but firmness ratings are very subjective anyway. There are no “standard” definitions or consensus of opinions for firmness ratings in the industry and different manufacturers can rate their mattresses very differently than others so a mattress that one manufacturer rates as being a specific firmness could be rated very differently by another manufacturer. Different people can also have very different perceptions of firmness and softness compared to others as well and a mattress that feels firm for one person can feel like “medium” for someone else or even “soft” for someone else (or vice versa) depending on their body type, sleeping style, physiology, their frame of reference based on what they are used to, and their individual sensitivity and perceptions. There are also different types of firmness and softness that different people may be sensitive to that can affect how they “rate” a mattress as well (see post #15 here) so different people can also have very different opinions on how two mattresses compare in terms of firmness. This is all relative and very subjective and is as much an art as a science.
Regardless of all of that though … as long as the firmness level works for you that’s all that really matters regardless of what anyone may call it 
Phoenix