That is absolutely not what they’ve said. What they’ve always said is that Standard Notes will remain a standalone project. It’s extremely implausible that Standard Notes features won’t also make it into Proton’s workspace services, while Standard Notes exists standalone.
Even if so though, Standard Notes itself is still a Proton product and even if it is never integrated into the Proton-branded suite. Proton’s still selling it as a service, and Shape’s knowledge base features clearly directly compete with Standard Notes itself, while other Shape features compete with Proton’s other offerings.