Help & troubleshooting for channels on your Roku device, including adding/removing channels, logging in to, authenticating, or activating a channel, channel-specific playback issues, assistance contacting channel publishers to report issues, and adjusting channel-specific settings.
The real difference between "BET+" and "BET+ on the Roku Channel" is that the former (BET+) is paid subscription directly to the provider and is generally available on any device. If subscribed to the latter (BET+ on the Roku Channel), then subscription is paid and managed by Roku and generally requires the content to be watched on a Roku device or at least through the Roku Channel on another device (phone/tablet.)
The content available on each is provided by the Channel provider/developer (in this case BET+). As such, best course of avenue for you is to contact the Channel developer and let them know of the issue and disparity between the two. (https://www.bet.com/info/3ovkvs/contact-us)
A quick glance at their help/contact page does not indicate that there is any difference in content available. However, since BET is available through cable providers (managed by CBS Viacom) and that BET is available with a Paramount+ subscription also, likely that you may have run into the issue that others have. Sometimes the content available to the subscriptions through cable providers are not available in these "+" subscriptions or is available later (updated/shown after they have aired on cable, perhaps next day or later).
I think best answer will be provided by using the "contact us" link above.
Roku Community Streaming Expert Just another Roku user... I am not a Roku employee. Insignia RokuTV, Ultra 4660x, Premiere+ 3921, Express 4k+ 3941