Titanium scraps can be recycled, although there is a cost in doing so. I think an additional reason is 3D printing may allow parts to be created with less titanium. They can have hollow areas or achieve shapes that milling can't.
My concern would be in part strength. AFAIK, 3D printed metal is typically weaker than forged and milled metal. Maybe things have progressed or these particular parts don't need "full titanium" strength.
Titanium is also a pain in the butt to machine. We figure 2-3x more machining cost compared to the same part made of 403/420/422 stainless.
This part of the article is particularly informative-
General Electric Co is already printing metal fuel nozzles for aircraft engines. But Norsk and Boeing said the titanium parts are the first printed structural components designed to bear the stress of an airframe in flight.
Gas turbine fuel nozzles are a very complicated shape and have relatively thin walls. In other words, a nightmare to machine conventionally. They have to withstand very high temperatures, but mechanical stress is low. Additive manufacturing makes a lot of sense for these parts.
Load bearing parts, on the other hand, will have higher mechanical stress, and traditionally this is where additive manufacturing is vastly inferior to traditional manufacturing. It may also prove much more difficult to inspect the parts. You can 3d print a beautiful part with a complex hollow or honeycomb shape designed to keep material costs to the absolute minimum, but how do you inspect it? Magnetic particle Nondestructive examination (NDE) is not viable, since titanium isn't magnetic. Ultrasonic NDE inspection doesn't do well with complex shapes due to all the odd reflections generated. Dye Penetrant NDE will only find surface defects. The only other reasonable option is Xray NDE, which is fine for some parts, but very difficult if the geometry is too complex.
With a conventionally manufactured part, you normally inspect the billet or bar before starting machining. With additive manufactured load bearing parts, there is no easy inspection method, either during manufacture or in-service, for complex geometries.