Right - you can treat the protocol as having:

1. Initiation (QR code, NFC in draft)

2. (Proximal) negotiation (BLE key exchange)

3. Communication (over websockets or a direct L2CAP channel)

The challenge is that a devices without bluetooth (at least today) don't have another common way to wirelessly judge proximity. A desktop/laptop without bluetooth likely either doesn't have NFC, or has bluetooth disabled by policy and would likely have cross-device passkeys disabled by policy as well.