There are two main issues. The first one is using numbers from your Social Security statement. Your Social Security benefit is expected to grow with the additional credits you will earn in your future employment, while your Social Security statement reflects only credits you have earned to date. Using values from your Social Security statement may be appropriate only if you are just about to retire.
The second issue is far more subtle, but equally misleading and inaccurate. Even after factoring your future credits, we need to also factor projected future changes in the Average Wage Index, the Taxable Wage Base and the cost-of-living adjustments applied to your future benefits. The Social Security Administration (SSA) publishes their own assumptions about how each of these items is expected to change in the future. These assumptions are based on considerable economic research and can be expected to be reasonable. The SSA uses these assumptions in their online calculators, if you select "future (inflated) dollars". This is the appropriate number for retirement planning calculators, because everything needs to be projected with its appropriate increase rates, as we discussed in the inflation section above.
Estimating your Social Security benefit using "current dollars" may be helpful in isolation — to give us an idea of the magnitude of our future benefit. But in a retirement planning calculator, we need to be consistent and increase every piece in an appropriate and reasonable manner. Most calculators that claim that they calculate your Social Security benefit from scratch, use a "current dollars" approach, resulting in a benefit estimate that can be half of what it may be reasonably expected to be.
MoneyBee projects your Social Security benefits with the "intermediate" assumptions from the latest SSA Trustee's Report. In fact, apart from rounding, MoneyBee should exactly match any SSA calculator on "future (inflated) dollars" basis, if using the same pay history.