People can stretch the definition however they like since there is no hard acceptance of where the line is drawn. Sure the general term musician means a person who plays/creates music. A person who hums can be a musician.
However in my own opinion, I disagree. DAWs are not instruments in themselves. The main functionality of a DAW is in recording, arranging, and mixing audio. They are the digital equivilent of a tape recorder and manual cut/splice process. They have evolved to include many software add-on emulations of instruments and packages around the production process: synths, pianos, mastering tools, additional recording tools, etc. Using a DAW does not make you a musician, but using provided instrumentation in a DAW can make you become a musician.