I watched the Blu-Ray and tonight tried the DVD and found it would not play because it is Region 2, unlike the 2 Blu-Rays. Seems Arrow screwed up.
shareMine was not even region 2, it was region 0 and it took me forever to find that out because for some reason my PS4 did not naturally play region 0 without physically changing the region. WTF? Arrow seems all over the place with this one.
shareThat's completely normal. Plenty of American Blu-ray/DVD combos have a region-free Blu-ray but a region-locked DVD.
The Arrow DVD will have been encoded in the European PAL TV format, which has slightly higher resolution but a lower frame-rate than your NTSC format. PAL-encoded video material doesn't play nicely with most standard American DVD players or screens, which will be why they region-locked the DVD.
Even if the region-lock wasn't there, chances are the disc probably wouldn't be viewable anyway.