Unavailable Mobility measurements

Dear Sir or Madam,

With regards to MOBILITY measurements, Apple watch ⌚️ records stair speed data completely fine : it's consistently available in HEALTH app after I go up or down the stairs.

However, because the other mobility metrics besides stair speed are interesting to track, I'm bummed they're not working at all. No data gets recorded or displayed in the HEALTH app for :

• double support time
• step length
• walking asymmetry
• walking speed

Could you please enlighten me on this technical issue? I searched the various settings but i can't find out a way out of this problem.

PS: I do see a measurement of the metrics mentioned above for February 15th but the purchase date of my Apple Watch ⌚️ was March 30th which makes me wonder. How is this possible?

Looking forward to your explanations. Thanks in advance.