us-core-1 is incorrect

Change from :

$this is DateTime implies $this.toString().length() >= 10

to

$this is dateTime implies $this.toString().length() >= 10

for details see this chat: https://chat.fhir.org/#narrow/stream/179266-fhirpath/topic/missed.20this.20in.20R5.3F.20vitals.20profile.3F