Softness aside, what are the characteristics that showed it to be a lowish quality steel?
... Really?
The fact that it is soft.
Kitchen knives should not be soft unless for specific uses, like cleavers or cutting frozen goods. In those particular examples a softer metal can be beneficial, as they're less prone to breaking and/or chipping.
They list a rockwell of 55 +-2 on their website for the x50. So it could be as low as 53. They don't divulge the specific type of steel they use which is a red flag, although they likely use x50 cr mo v15 which has a maximum hardness of 56 Rockwell. A kitchen knife with a 53 rating will take a very fine edge, for about an hour of use and after that will need to be sharpened.
In a home kitchen, that may not be an issue as it will only be used for a few minutes at a time. But in a professional kitchen, it's an absolute PITA.
My Aogami Blue goes 2 months between needing a sharpen, not 1 hour.