I never said that and neither does the FAR, posted again below. Pay particular attention to 25.175(b). The Boeing 737 MAX is unstable because in certain climb profiles, it will NOT "return to within 10 percent of the original trim speed when the control force is slowly released". The plane would climb until stall without the MCAS system stopping it.
Appendix: Federal Aviation Regulation Airworthiness Criteria Sec. 25.173 — Static longitudinal stability.
Under the conditions specified in §25.175, the characteristics of the elevator control forces (including friction) must be as follows:
(a) A pull must be required to obtain and maintain speeds below the specified trim speed, and a push must be required to obtain and maintain speeds above the specified trim speed. This must be shown at any speed that can be obtained except speeds higher than the landing gear or wing flap operating limit speeds or VFC/MFC, whichever is appropriate, or lower than the minimum speed for steady unstalled flight.
(b) The airspeed must return to within 10 percent of the original trim speed for the climb, approach, and landing conditions specified in §25.175 (a), (c), and (d), and must return to within 7.5 percent of the original trim speed for the cruising condition specified in §25.175(b), when the control force is slowly released from any speed within the range specified in paragraph (a) of this section.
(c) The average gradient of the stable slope of the stick force versus speed curve may not be less than 1 pound for each 6 knots.
(d) Within the free return speed range specified in paragraph (b) of this section, it is permissible for the airplane, without control forces, to stabilize on speeds above or below the desired trim speeds if exceptional attention on the part of the pilot is not required to return to and maintain the desired trim speed and altitude.
[Amendment 25–7, 30 FR 13117, Oct. 15, 1965]
You’re dancing around. The 737 MAX is aerodynamically stable. Because in extreme maneuvering that will not be encountered if the plane is flown properly within its specified envelope, the 737 MAX is not stable enough to meet the criteria of the FAR. That doesn’t mean the 737 MAX is an unstable design.
It’s like if a sports announcer said a driver did not meet the qualification time, you would take that information and then tell someone the driver was going in reverse.