There are several threads here on the forum about UP Aqua Shrimp Sand. Here's a link
to UP's product page. Definitely buffers.
I wouldn't use it in a tank that had so much plant mass that a dry start was necessary. There are better substrates for plants on the market that cost a whole lot less.
A lot of people who sell the product would have you believe it's miracle dirt. While it's a great product, it's pretty easy to find cheaper alternatives.
Does the shrimp sand you are using have any buffering capabilities? Would you recommend it for a dry start application?