I have done PDX/PVG/LAX/PDX, never on that segment have I been asked to size or check my roller. I travel with a backpack and at the time a domestic roller that didn't fit the sizer. These days go in Grp1 and generally haven't hear or seen them run out of space on the domestic. I actually don't have an issue that they would enforce, just do it across the board. But again what if they force check and there is lots of empty overhead?
On a PDX/PVG/SFO/PDX the UA GA at SFO on my return in a full flight was insistent that I size my roller. It didn't fit, like my 10th or 12th trip on UA but she wasn't going to budge insisted on me checking, no amount of pleading was going to change her, she dug her heels in! I was the 1st inline in Grp2 and I'm sure she wanted to make an example of me. Was really nice to wait for my luggage for 30' after midnight in PDX. I later saw multiple folks come on after me, clearly after Grp2 with larger and sometimes 3 bags. I was later told that SFO was very strict, YMMV.
Its UA, you expect consistency of policy and enforcement, LOL. I have no problem checking but consistent enforcement please, or be explicit on who gets the exemption. I think its a larger cultural and discipline issue. Maybe the leadership will learn someday that starting with the customer facing folks if they pride themselves on customer service with consistency and fairness they might actually do better than expected
