String orchestra uses solo instruments
S5 - Suggestion
When you create a score using the String orchestra, the instruments are the solo instruments (Violin, Viola...) rather than the sections (Violins, Violas...). String orchestras normally consist of sections rather than soloists. Though this doesn't make a difference using the MuseScore HQ sound font, there are sound fonts that do distinguish between solo and section strings.
IIRC it does make a difference with the HQ soundfont too