Lakemaster and Navionics both provide Pool 4 as a surveyed body of water. Having said that, keep in mind that this is a river system with an ever-changing bottom, so depths are reasonable estimate at best. The accuracy in both chips is NOTHING like you’d see on a major lake, like Mille Lacs. And that’s coming from someone who spends a lot of time on Pool 4.
I own both the Lakemaster (WI and MN) and the Navionics chip. Right now, I have the 2 lakemasters in my console GPS.