I pestered Parallels support for an update (it'd been 6 weeks since I heard anything about the issue) and got a response this morning:
Hello Stephen,
Thank you for following up on the investigation of the issue you've reported.
We've checked the status of the investigation and can inform you that according to the available information the issue will be fixed in the upcoming Parallels Desktop 14 update.
Due to the fact that the Development team doesn't share ETA for the release of the update the Support team cannot provide you with ETA respectively, regrettably.
From our side we can advise subscribing to the article mentioned below to receive a notification when the update will be released:
http://kb.parallels.com/en/124521