That should be correct. Because... you don't actually own the Legacy Pack DLC.
The Legacy Pack DLC is for those who own both the full HITMAN game + the GOTY content. You only own the first.
To quote the Steam page:
«This is the full Legacy Pack, which includes all remastered locations and missions from Season 1 and The Game of The Year Upgrade.
The bundle includes:
- All content from Season 1
- The Patient Zero Bonus campaign
- 3 Themed Escalation Contracts
- 3 extra Outfits
- 3 extra Weapons »
For example, I own the GOTY edition of the previous game, and on the Steam store, I'm marked as owning the Legacy Pack DLC.
Since you only own part of the content, you have a cheaper upgrade option, so that you can get the missing content.
That's why there's two options.