Thunderbolt to DisplayPort cables aren't a thing. Thunderbolt 2 was already a Mini DisplayPort connector that used normal cables for that; Thunderbolt 3 uses USB Type C and you can get USB C DisplayPort cables (using DP alt mode). No Thunderbolt features involved there either.
Converting Thunderbolt to DisplayPort is technically possible, but completely pointless because both TB2 and TB3 are natively DisplayPort compatible, at both protocol and connector level.
> Converting Thunderbolt to DisplayPort is technically possible, but completely pointless because both TB2 and TB3 are natively DisplayPort compatible, at both protocol and connector level.
One exception: it's useful for a Thunderbolt Dock to have a Thunderbolt connection to the host system, while offering another Thunderbolt port that can emit a standard, un-encapsulated DisplayPort signal. But for an adapter with none of the other ports offered by a dock, it is generally pointless.
Converting Thunderbolt to DisplayPort is technically possible, but completely pointless because both TB2 and TB3 are natively DisplayPort compatible, at both protocol and connector level.