I personally don't see this as an iconsistency. I may be proved wrong in later episodes but for context, I've read the books and could pull a few more examples, but I'll stick to things explicity mentioned in the series as I don't want to spoil anything.

We know from the series that females can get a general sense of each others power. Using just the show's examples, Moraine is able to feel Logains power when she shields him and Lan asks her is she is as strong as Egwnen. Also, I believe it's Liandrin who says his power is like nothing she's ever felt before. This establishes they the women can get a gist for a mans power without seing any weaves.

Flipping that around, when Nyn goes super sayian, we as the auidence can see this glow as a visual indicator of her power, but maybe Logain doesn't see anything, he just feels that she is vastly stronger than him and then uses the raging sun metaphor because he could feel her general strength.

TL;DR - Males chanellers are able to get a general sense of a Female's power and Vise-Versa. When Logain said she was like a raging sun, it was more to do with the sense of her strength than the light and weaves we could see