Shmuel vs. a Tanna

In Brachos 23b, the gemara quotes a braisa which proves Shmuel wrong when he said that you could put the tefillin in your bed even when your wife is with you. Rava said that despite this braisa we pasken like the Amora Shmuel. Then on 24a the gemara quotes a machlokes between Rav Yosef and Shmuel whether you can say Shma with others in bed. There is a braisa that seems to contradict Shmuel. Rav Kahana asked Rav Ashi if Rava would say the same thing here that we pasken like Shmuel against the braisa. Rav Ashi said obviously not. Rava said it there so he meant it only there and it can be applied elsewhere.

The Rosh asks why over there would we pasken like Shmuel against a braisa but here we wouldn't. He answers that Amoraim in general are allowed to argue with braisos because they can always say that the braisa is meshubash. We can still ask questions from braisos on amoraim because they can only say that if they'd seen the braisa and then disagreed despite the fact that a tanna said otherwise. In the case on 24a though it seems that Shmuel hadn't seen that braisa so in that case if the braisa disputes him then it proves him wrong. This explains why throughout Shas we are able to ask questions on Amoraim from braisos and we don't always answer that the braisa is meshubash.

The only question that remains is what was Rav Kahana's hava amina? He obviously knows that a braisa normally would "win" against an amora. Rava gave a svara over there why we pasken like Shmuel despite the fact that the braisa was against him but lacking a strong svara we would not pasken like Shmuel against a tanna. I was thinking that perhaps Rav Kahana thought that Shmuel could win against a Tanna. We know that the gemara often says "Rav tanna hu u'palig" and Shmuel is the same generation as Rav and we actually pasken like Shmuel many times (dinei mamonos) against Rav. So Rav Kahana thought that perhaps Rava was saying that we don't care about braisos that contradict Shmuel because Shmuel also "tanna hu u'palig." Rav Ashi answered that we don't say that about Shmuel. Only in that specific case did Rava say we pasken like Shmuel against a tanna but in normal situations (where we won't say the braisa is meshubeshes and there is not an overriding svara) we will pasken like a tanna against Shmuel.

I'm not sure why we say Rav is considered like a tanna but not Shmuel. The truth is that I thought we did say it by Shmuel also but I can't find anyplace that we do so now I'm assuming that we don't. If someone knows otherwise please let me know.