Correct, SPG transfer to CO and US at an unattractive rate, probably to protect Chase from competition. (Chase is the bank that issues both CO and UA mileage credit cards.)
Converting ThankYou points to giftcards, on the basis 20,000 = $200 is far from the best value, because 20,000 TYP = one domestic ticket worth up to $400.
SPG also has an annual fee of $45.