That's always the concern with privacy-focused services, especially if they're not open source or audited.
But if we think about the practical application -- who needs a honeypot for cell phone services? Carriers already collect so much data (location, telemetry, payment, government-issued ID, etc) and sell it willingly to whoever wants to buy. How could Cape be any worse? lol. If they adhere to any of their stated policies it seems like a plus, no?
Additionally, at least to me, Cape is not marketing the way the Anom phone did, where it trying to gain adopting by nefarious users. That's my take - I'm not advocating for Cape since I don't really know much about them, but I'm trying to put things in context.
You get you phone number through them and they act as your carrier and then they use other telcos that have the physical infrastructure to service calls/data. Not that different from how Mint or other virtual networks operate, but Cape alleges to collect little data about its users and not to sell any user data.