Nothing in the post you're replying to is about "is 2000 passkeys storable", it's about "if I have 2000 passkeys and I need to move between an Apple device and an Android device, do I need to establish a second set of 2000 passkeys"?
No, the majority will not. If through some miracles, passkeys gain sudden and wide adoption, there will be a day of reckoning come around the next mobile refreshment cycle, maybe earlier.
People break their phones. That is normal experience. Entirely unsupported by passkeys as they are today.
I'm actually surprised we didn't have more pushback for ubiquitous 2FA, as they have similar threat profile - i.e. addressing the tin-foil threats of cybersecurity aficionados, while entirely ignoring the common threats to real people, in particular the one of broken or lost mobile device.