See "Big Three of Shatin" (Tai Wai, Sha Tin and Fo Tan) all only has `highway=tertiary` to connect to them. There are more similar examples.

CPR (Ko Po - Ngau Tam Mei) tends to use Yuen Long Station instead. (See KMB 76K, and the many minibus routes.) Northern Link (construction is starting) is reducing importance of KSR station in terms of actual passenger in-out count via KSR station; would go in/out at Northern Link stations instead.

I understand Pat Heung Road gets `=secondary` because it needs to connect with Kam Sheung Road, which is itself uncontested `=secondary`.

imo this is OK-convincing but not ultra convincing, but perhaps @Kovoschiz may have something to say?