Product thinking is a more holistic view than UX/design thinking… and it’s also much more complicated.
I’ve been both a product designer and a UX consultant, and when you work in product design you have to think about a lot more than just the end user needs and the UI (or creative) design. You have to look at the business drivers and goals, competitive landscape, the hard “costs” around the feature set (whether it is a physical or electronic product), and how to message/market the product to existing or potential customers.
Product design is a lot like service design, in that there is a lot of “backstage” processes/moving parts that has to be defined and supported to provide the “front stage” experience to the end users. Traditional design thinking has tended to focus on the “front stage” stuff, and thus has less awareness of what is needed to bring a proposed design to life. There are exceptions, of course – I’m speaking in generalities.
If we stay in our UX design “silo” we will reduce our opportunities and understanding of the business… and risk being viewed as “nice to have” rather than a key part of the process.
UX design is often a phase in a project – product design IS the project, and the more UX practitioners move to a product design model the more involved we will be in the definition and implementation of solutions for end users – and we will have a bigger impact when it comes to bringing usable solutions to market.