The Product Manager working within a SAFe® portfolio is also the champion of the product. Dean's point stands here as well below.
"The PO represents the interests of everyone with a stake in the resulting project...achieves initial ongoing funding by creating the initial requirements, ROI, objectives and release plans." - Schwaber 2007.
As pointed out by Dean Leffingwell, "the product owner's responsibilities don't end with the previous broad statement."
There must be a dual role capability at scale in a large enterprise to dissolve the inherent conflict created by a member of the team driving requirements as the proxy to the customer (the PO). This is accomplished through the Product Manager role separating duties from the PO.