Weird, just spot checking a few places I know relatively well I see a few issues that seem like they would show up from that method. I wonder if there are issue in build up environments? Unfortunately that link is down for me.

A collection of streams go uphill in this map where in reality I believe they flow into an underground pipe or something that drains into the lake in a different place. I wouldn't expect the underground section to be perfect, but the hill the streams ascend is ~50 feet.

In another place two ponds are not shown, maybe due to dense tree cover? I believe both have water year round, but one was fenced off after a kid drowned and the owners may have filled part of it in.