I did a search on 'sweet peet' and found the following news article:
...snip..."Their patented process uses tannins (plant extracts) to convert shavings-based horse manure into a high-grade coffee-colored mulch called Sweet Peet.While it's not intended as a soil amendment, the lime added in the conversion process helps counter low soil pH caused by acid rain across the U.S"

Since this company is based in the East, acidic soils might justify adding lime, but in areas with alkiline soils that seems problamatic.

Here is a link that might be useful: Manure becomes money for Sweet Peet

I have never used sweet peet, but it looks like a fancy compost to me. I make my own.

Use your own garden soil to pump up your microherds good biological activity in your compost pile. Check any mill where they make up animal food to locate Black Strap Molasses. Black Strap Molasses animal feed quality is the best booster and the cost is minimal. You will need to have your own gallon jug. You may have to explain "for garden use".

Sweet peat is one hundred percent plant parts. It is not considered to be soil. It can decompose over time and become part of your soil. If something has been added to make it sweet that would have to be on the label..

What do you mean it's just dirt? My obsessive behavior over the last few months, relegated to just dirt. OUCH!
Just kidding.
Never heard of sweet peet, but there is a similar product down in my area called royal soil. It is composted horse manure, pricey, but well worth it if you don't compost yourself, I'm not sure if they add lime to theirs or not. I do know that they have been featured on Volunteer Gardener, and that they have people from hundreds of miles who travel to get some of it. It is heavily used at the state capital, and I have to say their gardens are very lush and gorgeous. If lime is added, I'd test your soil ph prior to using it.