When making repro's the designs are often a whim of the designer.
Yep, absolutely, reproductions often have 2 or more design styles within the same piece. Matter of fact, in late victorian (american) period furniture, sometimes they had 3 or 4 different styles in the same piece, it was almost like furniture makers were throwing all those designs against the wall in the hope that one would catch the eye of a buyer.
If it was me, I'd try to identify what design element on the sideboard tripped my trigger, the legs? (elizabethan) the drawer fronts? (jacobean/mannerist) and go from there in trying to find something that worked for me.