Financed emissions - Sector definition

For a financial institution setting its Scope 3 Cat 15 Investments science-based target by sector, is it mandatory that the sector classification for the investment/lending portfolio to to follow the proposed sectoral scope by SBTi ? (E.g. The proposed sector scope in the “Guidance on setting science-based targets for Oil, Gas and Integrated Energy companies” using the Oil & Gas sector as an example)

Or the financial institution has the flexibility the decide what is in scope vs out-of-scope as long as the approach and coverage is clearly documented?