They are different displays, but mainly it is a construction "artifact". LEDs only produce light at the point where the current flow drops due to hitting a small amount of semicondutor material - releasing energy as light. Tthe manufacturers have tried different shapes and substrates to make the displays more legible, help dissipate heat(substantial) and avoid light being reabsorbed by the semiconducting material. The modern trend is to make the LEDs smaller and brighter, and then magnify them up to the size desired. Not as soothing to look at as the early dot displays, but much more energy efficient.

The heat they produce is amazing!
http://www.retroleds.com -
Sales of vintage LED, LCD, analog watches,
parts and gadgets -
repair tutorials & tips
Nov. 2022 - back in business!! BItter divorce is in home stretch, come grabs some great deals, I had to open the safe . . . damn attorneys. piss.