How do I close log files that are open in OracleServiceORCL after inputting data into Oracle?
Well, its Oracle on Windows, such issues are not uncommon there.
Similar, but not exactly your issue:
Bug 30191227 - HANDLE LEAK ON EXTERNAL TABLE LOG FILE IN WINDOWS PLATFORM
No fix exists yet for it, not even in 19c. Suggested workaround:
WORKAROUND:
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Manually release the file handle using Windows process explorer.

Of course database restart works as well (Oracle on Windows runs as a single process).
Process Explorer