Repro Steps:

1) Create new sandbox with CH version of BC25.2 and open chart of accounts

2) Enter the currency code EUR for account 1026 and the currency code USD for account 1028

3) Make postings to account 1026 (with currency EUR and blank) and account 1028 (with currency USD)

1026 with (EUR) amount of 100 and another line for the same G/L with amount of 1.18

1028 with (USD) amount 200

4) Check G/L Accounts 1026 and 1028

Source Currency Posting for both has ( Same Currency)

5) Check G/L Entries of accounts 1026 and 1028 - Correct

6) Check Source Currencies of accounts 1026 and 1028 - Correct

7) Activate new feature (and migrate G/L Accounts and G/L Entries)

8) Check G/L Accounts 1026 and 1028

 1026 has Source Currency Posting of " Multiple Currencies" - Incorrect

9) Check Source Currencies of accounts 1026 and 1028 - Incorrect for 1026

10) Check G/L Entries of accounts 1026 and 1028 - Source Currency Code for 1026 has no code.

Expected Results: 

The Source Currencies and the General Ledger Entries and the Source Currency Posting should be the same as before enabling the feature.

The product team has confirmed that this behavior is by design.

One of the partners has reported that this could lead to significant issues in the future, as partners might not be able to reverse the effects of the feature on the Source Currencies table, G/L Entries table, and the Source Currency Posting field in the G/L Entries table.