its implied. Obito couldn't use it either. And if they had it, they'd know how to use it.
Unless it was an MS jutsu, Madara taught Obito the Rikudo jutsus so why not teach him limbo if it's a Rinnegan jutsu? He taught Obito stronger jutsus than limbo such as the 6 paths jutsus, 7th path (outer path), summoning the Gedo, use any element with the Rinnegan, use yin yang jutsus. Now I'm not saying Limbo was of the same caliber at MS, Madara got Hashirama cells which shown to increase jutsus effects/power/usage such as KA needing 10 years to recharge but Danzo being able to use it once every few hours. Plus The Sage Senjutsu increases the eyes powers as it gave Obito's eyes the ability to skip to EMS status and use PS.
People think if Madara had it that he would beat Hashirama but how does that mean he can beat Hashirama? Madara took hits from the Bijuu's and didn't flinch to the pain plus he has Hashirama's healing; Hashirama has the Sage's body and his healing, he can definitely take hits from Madara and get back up. Also Madara have a time limit of how long Limbos can be out and a wait time before using them again. It would explain how neither Obito and Nagato had it and Nagato had the Rinnegan for like 20 years