Deus Ex Collection: Steam vs Humble Bundle

Check the one on steam. For me it has been updated to a bundle not a pack which means you can not buy it as a gift.

EDIT: The one linked to SG which you would have to purchase from somewhere other than Steam. https://steamdb.info/sub/15147/apps/

The old one is bundled, the new one isn't. The old one is significantly cheaper though.
Edit: Oh, yeah, the new one is a Steam bundle. Cannot be bought as a gift.

SG lists only this old one: https://steamdb.info/sub/15147/, which doesn't seem to be equivalent to the one on HB but isn't equivalent to the new steam one either. HB one has Deus Ex: Human Revolution - Director's Cut and Deus Ex: The Fall (like this package) while the SG one has Deus Ex: Human Revolution + DLCs instead. You might wish to ask support about it and maybe ask to add another ID to the list.
Since the new steam one is a bundle and not giftable, there is no need for it to be listed on SG until it appears in another store with the same content.

interestingly, if you own even 1 single Deus Ex game, getting Mankind Divided + Season Pass is more expensive than the Deus Ex Collection bundle

The entire bundle, if you own nothing, is $93.75, whereas Mankind Divided + Season Pass is $89.98