getSwappingPrice() is intended to get swapping price between to underlying assets in the tranche but this function and its implementation doesn't make sense when only one ERC4626 is deposited into the tranche.
Technical Details
The Gro protocol as examined only has one token that is deposited into it, as the return value of getYieldToken() shows. The current implementation of getSwappingPrice() allows any uint256 input values for function arguments i and j and always returns the input _amount which implies a 1-to-1 exchange rate between token i and token j. This return value doesn't make sense. It would make more sense to follow an implementation like getYieldToken() shows and only allow an i and j value of zero, reverting in other cases.
Impact
Informational.
Recommendation
Consider a different implementation for getSwappingPrice() rather than returning a value that assumes a 1-to-1 exchange rate between arbitrary input tokens. The function is not called by the existing Gro implementation so it is not very important.