The issue is that calling might yield one answer thar could differ from what you experience "on the ground."
So true. Results can differ depending on the gate agent, but I have never had them refuse my bike. The biggest thing I'd say is be sure it meets weight and dimensional limits.
For a long time I tried to just have the bike and little seat wedge with some tools and repair stuff in the box. In one case the TSA opened the seat wedge dumped out the contents. They then ripped out the stiffener of the bag, I guess to see if amything was hidden there, or maybe just to be jerks. All the stuff from the bag was loose in the box.
I have more recently (since I started packing really light) packed all of my gear in the bike bag camping gear and all. That was with a soft case and UL gear made keeping it all under 50# possible. There was no sign they even opened it on either leg of the trips (two trips packed that way definitely were with delta). It was really nice to have just one checked bag with a shoulder strap. I did also have a little personal item sized backpack but could have gone without it.
I have generally attached pedals and so on with cable ties so they didn't get separated from the bike.
The majority of the time I don't think my box has been opened.
None of that was recent. Also any problems were I had TSA related and happened after the bike was checked and out of my sight and really had nothing to do with the airline. The gate agent just asked if it was a bike and weighed it. Usually they didn't measure it, but I wouldn't count on that.