It's the transit type that matters: standard transit gives longer jump shock than squadron transit.
Commercial jump drives do not give longer jump shock than military jump drives.
But commercial drives are usually used for standard transits, and commercial jump drives have their squadron size reduced by 1, so we have the impression that commercial drives themselves are less suitable for low-shock jumps.
If you are planning a jump assault with 28kt ships, might I make a suggestion?
Split your 28kt design into two designs.
Put the engines and the fuel into one design, and add a tractor beam.
Put everything else into the other design.
You can jump the engineless portions with a commercial jump drive, have your battle, and then jump the engine portions.
You get to use a much smaller military jump drive, since the engines and fuel are probably about 1/3 of the overall size
And since you won't jump the engines in until the battle is over, you can jump them via standard transit, and use a separate tender for the military jump drive
Of course, your engineless portion has a speed of 1, which means it is easy to hit, will need energy weapons to be turreted, etc.
A design dedicated to jump point assaults probably doesn't need to rely on speed anyway, but it depends. If your design needs to stay at the closest possible range, this approach is not viable.