The linked article’s optimization applies to compound index queries, not “OR” condition optimization. Unrelated or not, skip-scan will be useful in some cases.

The linked article’s optimization applies to compound index queries, not “OR” condition optimization. Unrelated or not, skip-scan will be useful in some cases. However, the cases where it adds noticeable benefit are the cases where a separate index should have been used for leading columns anyway (and in memory-constrained/frequently-cold-cache situations, a separate index might even be faster). If you can’t even begin to guess at the order of magnitude of cardinality, or if your leading-column-lacking queries are quite rare and not that perf-sensitive on a big table exerting index cache pressure, then skip scans make sense.