A smart lock welds three disciplines to one door. There is the mechanism (a mortise lock body and a motor-and-clutch that throws the bolt), the credential stack (how you prove who you are), and the cloud (how it talks to a phone). The reference design you buy is really a choice of which credential modules and which app platform a house has already integrated, the casing is the easy part.
The mechanism is the old trade. Mortise sizes (5050, 6085 and the European DIN profile), anti-drill panels, C-grade cylinders and salt-spray-rated housings come from a lineage that predates electronics by decades. Zhongshan, branded the country's Lock Capital, has stamped and machined this hardware for a generation; Shenzhen then bolts the electronics on. Most smart locks are that marriage.
Credentials are where the catalogue competes: fingerprint (semiconductor FPC or optical), a PIN keypad, an RFID/NFC card (13.56MHz Mifare), and the premium tiers now 3D face and palm vein, with a mechanical keyway and a USB-C jump-start as the fallback. The connectivity, Bluetooth, Wi-Fi, Zigbee and the emerging Matter-over-Thread, almost always rides a platform: Tuya (Smart Life) or TTLock / TTHotel. Few houses write their own cloud; they license one of those two.
Security is a standards game: EU EN 14846 plus RED for the radio, US ANSI/BHMA grading and UL, and China's Public Security Bureau (GA) mark. The houses below are the hireable layer beneath the brands (Kaadas, Dessmann, Aqara, Lockin, Philips, Yale and August under Assa Abloy). The tell of the rebadge: one Tuya-platform fingerprint lock sells under dozens of names.