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This approach essentially treats your migration from your source ILS as a point in time - e.g., this is where this fee fine is right now - and then FOLIO generates transactions as the fee/fine is handled going forward. This simplifies your migration approach.
Note that migrating only as an account and not also creating JSONs does break some functionality (as of Honeysuckle) - you are not able to see the Staff Info Only button, for example.
Migrating feefines as manual instead of automatic charges
You could consider migrating fee/fines from your system as manual instead of automatic charges. If you do so, the recommendation is to create a charge type for each fee/fine owner that can help you identify which fee/fines were migrated from your old system.