Worked out for me like so in the past couple of months. Bought UA ticket initially in R discounted PE operated by ANA on ORD-NRT. Upfared to A and changed flight # to native ANA whereupon fare code became E. Filled out the form for upgrading with PlusPoints. ANA app showed waitlisted initially, but it changed to Confirmed in Business within less than 2 weeks. This was even for Sakura season traveling on April 2. The ANA biz seat is wider than UA’s, which was sweet. Catering and service exponentially better.