Clinton won Maryland by 26 points, so this is pretty in line with expectations if a bit low, possibly a reflection of this pollster's pro-R bias.
What's interesting to me is that they have Biden winning black voters 86-8. No exit poll in Maryland in 2016, but PG county (61% AA) voted Clinton 88-8, meaning she probably was in the mid-90s with black voters... perhaps this number indicates some slippage for Biden. It could also just be a MOE thing.
Speaking of PG, one weird thing I noticed is that Republicans consistently get lower percentages of the vote there than in Baltimore City. This was true of Trump, Romney, McCain and even Hogan. What's the deal?
White liberals in the DC area are more Democratic than even big city Blacks.
This... isn't exactly right. PG County is dominated by middle-class blacks, who have pretty high turnout rates. Baltimore also has a large albeit diminishing amount of white ethnics (Poles, Irish, Italian, Greek).