Looks like when a Couchbase server is re-configured to be name-based instead of IP address-based, even the client’s configuration must be adjusted to match else it would fail to connect to the node. Wow.
<couchbase>
<defaultBucket>
<servers bucket="default" bucketPassword="pw" xdt:Transform="Replace" xdt:Locator="Match(bucket)">
<add uri="http://CBL2:8091/pools"/>
</servers>
</defaultBucket>
<diskBucket>
<servers bucket="Diskbucket" bucketPassword="pw" xdt:Transform="Replace" xdt:Locator="Match(bucket)">
<add uri="http://CBL2:8091/pools"/>
</servers>
</diskBucket>
</couchbase>