Naruto didn't have all of the Bijuus chakra until right before he met Hagoromo and Bee had a small amount of the 8 tails chakra but it never showed him talking to Bee; it shows the 8 tails say he'll go back to Bee who is still alive after losing his Bijuu and being cut off via tentacle. Yin Kurama even mentions Naruto having all Bijuus chakra in him now then he called out their names to summon them
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, so him not using because he lacked all 9 Bijuu chakra makes the most sense.
Also RSM is a mode Naruto gained after receiving Hagoromo's Yang chakra just like how Sasuke's Rinnegan came from Hagoromo Yin chakra. How do we know Hagoromo gave Naruto yang and Sasuke yin chakra? Simple. Ashura represents Yang and Indra represents Yin as Obito said when he told the story to Naruto, Kakashi, and Yamato. Hagoromo even said he gave them his chakra and didn't have enough to summon them back from Kaguya's dimension so needed the past Kages help. The Rinnegan is awakened when you have Indra (Yin) and Ashura (Yang) chakra to awaken Hagoromo's chakra (Yin Yang). Sasuke only has 1 Rinnegam because he only has Hagoromo's Yin chakra so Naruto does have Hagoromo's Yang chakra.
Naruto combines Hagoromo's Sage Senjutsu with Kurama's chakra for the mode, he doesn't need to use the Bijuus for that. He was in RSM even though he wasn't using them against Sasuke. So if he can use it against Sasuke then using it without the other Bijuus again shouldn't be an issue. Also Naruto is much stronger than he was before; KSM (full Kurama) is on BSM (Yang Kurama) level since it has double the chakra reserve and a much more powerful chakra. So BSM (full Kurama) power would be around war arc RSM (Yin Kurama) power. Also nothing says Naruto can't use the Bijuus chakra in his other modes or use Sage Senjutsu with KM or BM.