That's correct.
Foreign currency is an asset for CGT purposes - Section 532 TCA.
The location of this asset is deemed to be where the creditor is resident (i.e. Ireland in this case) - Section 533 TCA.
Gains on foreign currency bank accounts do not qualify for the remittance basis of taxation even if located outside Ireland.
I presume your accountant has allowed for the personal exemption against any gains:-
This page is an explanation of what is exempted from CGT