What would even lead you to that conclusion, Their investing money into it and it's PS4 exclusive on consoles. Of course they're publishing it,
He probably got that conclusion from the fact that Sony isn't publishing it.
The PC version is being published by Shibuya Productions, who are also supposed to be involved in funding the game. That is the only physical version being made. The PS4 version is digital only, where Sony allows independent studios to self-publish.
Sony doesn't own a stake in Shenmue III. YsNet does. SEGA still does as they still own the IP and are letting Suzuki use it. Shibuya Productions likely does as they're ponying up for a physical release. The only profit Sony will realize from this is the royalty fee they'll charge, just like every other game released on PS4.
If Sony were actually publishing it they would have said as much. They have no ability to do so and the entire structure of the game's release platforms, all of the media up to this point, and all of the legal rights to the Shenmue brand indicate that nothing has changed behind the scenes to alter that.
When people accept that Sony isn't backing Shenmue III and putting it on Kickstarter to extract massive profits maybe then they'll get the actual concept here. Shenmue III will almost certainly LOSE money for Sony. Lets say Sony contributes $10M total between development kits, technical assistance, marketing, and straight out cash. Then lets assume they make a far higher royalty on it than most games at $10 per unit. The game would then need to move 1M units on the PS4 for Sony to break even. The first game sold 1.2M, the second sold 400,000. So Shenmue III would need to sell on par with the first game, a state of the art headliner at the time for the Dreamcast, 14 years after the series was effectively dead for Sony to realize any profits in this hypothetical.
Sony isn't doing this for money. They're doing this for the PR associated with it. It is a comparatively cheap way to net a ton of good publicity with the avid gamer audience that has propelled the PS4 to #1 so far this generation.
Any future kickstarters they do will likely be built on the same premise.
Suikoden is an example that would make some sense as that is a core JRPG gamer sweetheart and would, in conjuncture with Persona 5, FFVII Remake, etc. make the PS4 the clear choice for fans of JRPGs, leading to 3rd parties still making JRPGs to skew heavily PS4, possibly even resulting in "free" exclusives, and maybe just maybe getting a bit of traction in Japan's gaming market.
If Sony did the same thing with WipEout though? That wouldn't really have much benefit. They own the IP, there is no need for a way to circumvent a reticent publisher to make it happen, and the simple fact is that WipEout would generate better PR as an unveiling coupled with actual video than as a Kickstarter.
Sony is using these Kickstarter collaborations the same way they're funding Street Fighter V, just on a less grand scale. Capcom was quite honest a few years ago in saying that SFV wasn't coming until the audience on next gen consoles was large enough. Sony threw them a bone to accelerate that timetable as their financial contribution effectively "bought out" Capcom's concerns about market size. Meanwhile Shenmue III is a title that would never be financially viable for any publisher. The combination of Kickstarter and Sony's contribution makes it viable as fans are willing to pay more than MSRP to make it happen and Sony is willing to literally give money and resources away in exchange for goodwill and "free" PR.
To put it most simply: heading into this E3 it was pretty clear that the most avid gamers were going to be coming out of the show complaining that Sony doesn't have enough exclusives in 2015. The mainstream gamer wouldn't actually care because it's got COD, Star Wars, AC, Fallout 4, etc.. But a lot of bad word of mouth could spread because Uncharted slipped and the Sony first party lineup was otherwise pretty damn bare to start. Sony backed Shenmue, unveiled TLG, unveiled FFVII Remake, and got partnerships with CoD and Star Wars to make everyone overlook their weak 2015 holiday lineup. So if Shenmue costs them $10M in sunk money but they keep good word of mouth and lead holiday sales when MS is pulling out Halo 5 I'm sure they'll see it as money well spent.