Why does Pearsall get overlooked?  

B/c it looks like stuff the...
B/c it looks like stuff George Jetson would have

The legs on that couch look...
The legs on that couch look exactly like the legs on the Warren Church Lane coffee table with the basket weave design.
http://furnishmevintage.com/livingroom/vintage-lane-perception-surfboard...

Should we contact this...
Should we contact this dealer and let him know he's got a Pearsall globe and not a "roplogle"? Do people really not understand that the company made globes for everyone but someone else designed the bases?
Too many players in the mcm dealer field anymore. I'm not even a dealer but I'd do a little research before I stuck a 1300 price tag on a globe. Walnut after market piece from Mexico in the 50's? Hmmmm. Wish people were getting better advice about their collections. Aren't the sellers on 1st Dibs supposed to be the experts?
https://www.1stdibs.com/furniture/more-furniture-collectibles/globes/mid...

.
Don't worry about it, the net is full of wrong attributed MCM items, if you really want to contact them all you will have a full-time job.
Estimated about 20% of all dealers are professionals, the other ones are home time dealers without any specific background and knowledge.
At least in Europe, I don't know the situation in USA.
So take it easy.

I personally
Dont think Pearsalls designs merit the same lauding as other celebrated designers. I see almost all of his output as either too derivitive of others works or too kitchy. I marvel that his pieces bring significant prices at times. Much of his work leans toward the world of multi tiered fiberglass shade plaster lamps and chrome and vinyl dinette sets for me. Training or not, I dont see his contribution to design history.

I guess
the direct answer to your question is that he did not contribute to the advancement of design in general. Rather he produced too many "in the style of" works to compensate for the few that were more specifically his own ideas.