Clustered indexes aren't fully searchable during an indexer cluster rolling upgrade

[rbal_splunk]

I am trying to figure out if, during a rolling upgrade, we guarantee searchability. If not what is the expectation?
The customer is following steps as per >https://docs.splunk.com/Documentation/Splunk/7.2.4/Indexer/Searchablerollingupgrade

For now we have 12 indexer's in the cluster, but we are planning to add many more as an expansion plan.
Customer expect during "rolling upgrade" entire data will stay searchable, please confirm the expected behavior????

[rbal_splunk]

Splunk has a bug to guarantee searchability during rolling restart. The BUG#SPL-168132:Clustered indexes aren't fully searchable during an indexer cluster rolling upgrade

This bug is fixed in 7.2.8 and 7.3.x