I just want to be clear here. You are using it with a host variable in Oracle? That will match the prepare with a ?. For example:

VAR Name VARCHAR2

EXPLAIN PLAN FOR SELECT /*+ index(a index1) */ name, age FROM people a
+ WHERE name LIKE :Name;
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Also, how are you verifying if the hint is being honored?

Update: Related: Where the advice to use DBI bind parameters can go wrong (long)