No, Glowforge is not technically a 3D printer. The technical name for the category of tools that includes the Glowforge is "CNC laser cutter engraver", but it is more commonly referred to as a "3D laser printer."
Laser printing or cutting is based on subtractive manufacturing, while 3D printing is based on additive manufacturing.
Mentioned in this answer
Glowforge
The 3D laser printer