We've had Lutino Cockatiels for 40 years, and it's almost impossible to tell the sex of Lutino's without a DNA test. Unless of course, they start to lay eggs. Our little Sully is now 5, we thought "she" was a he because her cheeks were such a bright orange and her crest was a very bright yellow, there were no bars on her tail feathers either. Wrong we were, she was very vocal with tweets and chatter, but said no true words. Actually the kids said she was "special" and that's why she didn't talk...LOL. We assumed "he" was just slow to talk or wouldn't talk. When "she" was 3 years old, she laid 6 eggs and that solved the mystery. Now, she lays eggs at random times, usually 6-7. She's always very social even when she is sitting on eggs. We leave them in her cage for about a 7-10 days then remove them.
She does put her little butt in the air, and her vent opens and closes when she is stroked anywhere on her body. I don't recall my males over the years doing that. So perhaps, Bunsen is a "she" and not a "he." My males all talked and whistled tunes by 9-12 months. Also, they were DNA tested, so I knew the sex from the breeders.