Phrase (Obs.value as Quanity) not behaving as expected

[jscherer-motivemi]

This CQL expression should return a list of values from Observation.value.value.

(Original):
define "Diastolic BP From Observations On Latest BP Date": "Diastolic BP Observations" O where date from O.effective = "Latest BP Date" return (O.value as Quantity).value

This above code returns an emptly list although there are Observation.value data.
When we changed the code to the snippet below, the CQL expression behaved as expected.

define "Dastolic BP From Observations On Latest BP Date": "Diastolic BP Observations" O where date from O.effective = "Latest BP Date" return FHIRHelpers.ToQuantity(O.value).value