One key difference between whatifi and your spreadsheet is data.
In a spreadsheet, every value is simply a number with a label in the next cell. Delete that column with labels and you’ll have no idea what the value represented.
In whatifi, we attach a bucketload of metadata to each value. Dates. Amounts. Ranges. And Account Types.
Much like an accounting package - we have a full chart of account and ledgers. We follow a fairly common framework for our defaults.