It does not work, throws different errors:
$ ledger reg Assets:Investment -p 2021 -X USD -M --gain
While calling function 'get_at (CAD 97.45000
-2,234.66891242292 USD, 1)':
Error: Attempting to get argument at index 1 from a balance
$ ledger reg Assets:Investment -p 2019 -X USD -M --gain
While adding (7.0 TLT {122.65000000000 USD} [2019-04-12], 7.0 TLT {122.65000000000 USD} [2019-04-12]) to (353.02000000000 USD, 353.02000000000 USD, CAD -104.80000
-440.13695725000 USD):
Error: Cannot add sequences of different lengths