To expand on my post above:
Nimbus have recorded the Symphony No.9, op.140 (2016) along with the Double Concerto for Violin, Viola and strings, op.122 (2013) and the Variations on Bach's Chorale "Die Nacht ist Kommen" for strings, op.40 (1986) with the English Symphony Orchestra under Kenneth Woods. The release is planned for "early 2019" (although one has learned to be cautious about such statements!).
Chandos recorded the Symphony No.8, op.131 (2014), "A Vision of the Sea" for orchestra, op. 125 (2013) and "Toward Sunrise" for orchestra, op. 117 (2011-12) in November 2017 with the B.B.C. Philharmonic Orchestra under Jac van Steen.
The first performance of the new Concerto for Orchestra, op.151 is planned for May.
There are only a very few, short orchestral works of David Matthews-mostly for small orchestra or for strings-which have not been recorded :)
Fascinating. It seems as though the industry records but waits until the maximum opportunity to release the recording. So we need patience.