Yes, power steering failure is a very serious safety defect.
Recommend you file a report with NHTSA ASAP:
www.safercar.gov
On a more pertinent note, our country (US) has a stunningly poor level of driver's education, especially as compared to Europe. Hence, the OP's feeling that the steering wheel "locked up" when, in reality, it was simply very, very hard to turn in his situation. Had he sped up, or applied more force, a near-head on collision situation would have been avoided. It was a very poor move to just let that sort of accident unfold due to a lack of knowledge of how non-powered steering works.
No Model X has a steering wheel lock, AFAIK, and never will . . . but it's what you end up with when there is nearly zero quality drivers education here.
p.s. And, a huge shame on Tesla for not improving the alert/warning for this failure mode. They really need to hire some Human Factors Engineers to explain to them how to rank order and alert for various failure modes . . . .