Unused indexes

For indexes that existed before the cluster was last started, and for which 
REINDEX hasn't been run on them since the cluster was last started... is it 
valid to say that an index has not been used since the cluster was started 
if these three pg_stat_all_indexes fields all have a value of 0?

idx_scan
idx_tup_read
idx_tup_fetch

If it matters, the version is 9.6.6.

Thanks

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