I did some serious digging into the design of the newer (2004+) 3v modulars requiring 5w20 and found the following engine components were exactly the same when compared to the 1997 5.4L modular engine(5w30/10w30 was Ford's recommendation back then),
- main/rod bearings
- hydraulic lifters
- chain, chain tensioners, and guide
- oil bypass valve (same relief value)
I looked thoroughly at a number of parts catalogs/service manuals (Motorcraft, Melling, Ford and retail autoparts, official Ford/Motorcraft service manuals). I also looked at bearing clearance specs, etc. The VCT system can compensate for higher viscosity oils because of the built-in feedback system (VCT solenoid/position sensor) that regulates oil flow into the VCT phaser. So it is not surprising that the OASIS report recommended 10w40 for excessive VCT noise. In fact, I read that low pressure to the VCT can cause it to rattle, making noise.
The main difference aside from the VCT system, is a higher volume pump to actuate the VCT's. There is also a pressure reduction into the heads (because high pressure pump feeding the VCT phasers) lubricating the cam, lifters, chain tensioners, and chain. The pressure to the VCT system is not reduced. So it appears the 3v modulars are versatile in regard to oil viscosity.
Not recommending that anyone not follow the manufacturers recommendation, but there doesn't seem to be any harm in running a 30 wt in these engines. Ford South America recommends 5w30 in this same vehicle/engine.