Yes, that's correct. If you are partitioned away from the lease holder, then you can't read until either the partition heals, or the lease expires and a new lease is granted to a node that you can reach.

Writes require the lease too, so it is not possible for a quorum of nodes on one side of a partition to serve writes while a lease holder on the other side serves stale reads. This is a degenerate case of quorum leases (https://www.cs.cmu.edu/~dga/papers/leases-socc2014.pdf) for a single lease holder; in the future we're interested in supporting multiple lease holders to improve read latency (at the expense of write performance and availability).