Only Marmot could confirm but they seem to match up, spec wise. Optima, per STP is 15 oz. wt., 27" length; Minimalist, per Marmot is 14.4 oz. wt. and 27.25" length. Otherwise, all other specs appear identical.
Pretty sure it is. Wore it on a hiking trip in Swiss Alps. Kept me dry thru hours of rain and sleet. Very satisfied.