Is purchase_title officially supported?

I'd like users to be able to update the Buy URL as well as the Buy Title for each track. As I'm working on the functionality, I'm finding some inconsistencies. It seems that the option to update a track's Buy Title is limited to certain accounts (possibly paid ones). Even on SoundCloud.com.

SoundCloud Next User - Updating does not work for this users

• PUT purchase_url does not cause an error
• PUT purchase_title does not cause an error
• GET users/{id}/tracks/{track_id} return contains updated purchase_url, but null purchase_title

SoundCloud Next Pro User - Updating works for this users

• PUT purchase_url does not cause an error
• PUT purchase_title does not cause an error
• GET users{id}tracks/{track_id} return contains updated purchase_title and purchase_url

This also seems to be the case on SoundCloud.com metadata editor. See screenshots below.

Is purchase_title limited to paid accounts? Is this a bug? Or is the purchase_title a field that is not officially supported and should be avoided?

@rahul-sc

Start by comparing the reported PUT and GET behavior for purchase_url and purchase_title across SoundCloud Next and Next Pro accounts. Review the public API behavior and the SoundCloud.com metadata editor evidence; done means establishing whether purchase_title is supported for all accounts, documenting the answer, or confirming a reproducible API defect.