here's why I believe this is the case:

1. Choco-sen has a surprising amount of streams together with Bancho, Ao, and Raden but I can't seem to find one where she collabs with Ririka? If anyone has a video where those two are together, please link.

2. When you search "Ririka and Choco-sen" on youtube, the first video you get is Miko talking about how Ririka sounds like Choco-sen in her younger days and then suddenly there's no other videos of those two being mentioned again or even the similar voice topic popping up anymore. Could it be that Miko at that time didn't know Ririka is Choco-sen and so she accidentally said that and then after when she got told, they asked them not to bring it up anymore?

3. This was the only clip I could find of Choco-sen speaking English (https://youtu.be/Iw3JrbS4nV0?t=85) and it surprisingly sounds very similar to Ririka's (https://youtu.be/XyeiQgAWpFQ?t=23).

I could probably try and find more "evidence" but there's no point. Someone just show me something to prove otherwise.