That isn’t my understanding at all.
What is converting the digital signal to analog, the Digital (to) Analog Converter, is absolutely what determines the quality of the signal. There is a DAC for the audio chip set in a laptop and it determines the quality of the output if you plug into the headphone jack on your laptop. If you are using an external audio interface its DAC determines the quality of the signal output.
I think what Artificer is getting is that unless you are used to ultra high end DACs and Speakers/Headphones working with the onboard DAC and headphones while you are out and about will be fine.
If you are used to using ~$100 headphones and an inexpensive audio interface I don’t think you’ll notice much difference between that and your onboard sound chip and your headphones. No headphones I know of have DAC, they only accept the analog audio signal after it has been converted. The reason to use an inexpensive interface is because it reduces latency.
I think the main point here is, on the go for composing, I wouldn’t worry to much about using the onboard audio chip set (unless you are used to using higher end gear).