I'm not sure what the motivation was to switch to LONG at that time, but already then, the type has been deprecated by Oracle for 12 years as has been mentioned before. It is not recommended to continue using this type in new tables:
https://docs.oracle.com/en/database/oracle/oracle-database/18/sqlrf/Data-Types.html#GUID-4C0B65DB-E751-4957-A1ED-5044BAFA7812

LONG Data Type
Do not create tables with LONG columns. Use LOB columns (CLOB, NCLOB, BLOB) instead. LONG columns are supported only for backward compatibility.

I strongly recommend reopening this issue and reconsidering this mapping for Oracle. Of course, the workaround is to add a @Lob annotation, but this is very easily forgotten, especially when an application supports several dialects - as few of the other dialects need the @Lob annotation.