Instant coffee is not generally considered to be the epitome of great tasting, or smelling coffee. It's almost the antithesis of artisanal whole bean arabica coffee.
The iconic and appealing smell of freshly roasted or brewing coffee is due to arabica coffee. Instant coffee though is mostly, and often completely, made from lower cost robusta beans. Robusta beans have a distinctly different taste and aroma profile.
And while industrial roasters have gotten very good at coaxing arabica-like flavours from instant coffee, the underlying qualities are still there and still noticed in the aroma. So the short answer is that your brand of instant coffee smells a lot more like typical robusta beans than the more desirable arabica beans.
Aroma is somewhat subjective and can be easily influenced by suggestion. I can understand your perception of soya sauce, although that characterization might be a bit off the mark. Soy sauce covers a large range but is something of an earthy umami aroma usually having malty seasoning, cooked potato, caramel, alcoholic, smoky or honey notes.
Myself I would describe the MH instant coffee aroma as bittersweet like the artificial sweetener, Sweet n low, sweet and bitter/metallic/alcohol aroma over a predominantly peanut and wet paper flavours.