Is a ballast required, or merely acceptable, for this Philips InstantFit LED tube?
Interesting thing about being human is the brain is wired to see what it expects to see.  It's hard to turn that off, even if you're a ship spotter or pilot. 

There is such a thing as LED bars which work both ways, either with a ballast or direct-wire.  But they're a lot bolder about claiming so!

The ruling word is "only" and your first interpretation is correct.

The data sheets you link are highly ambiguous. But that's not so weird when you look at the Electrical Code, NEC 110.3b:


  NEC 110.3(b) Equipment must be installed and used in accordance with any instructions included in the listing or labeling requirements.


The operative words are instructions and labeling.  A data sheet is neither. 

So you need to review the labeling on the item, or the instructions in the box. 

Be warned: if you find that data sheet inside the box, that is bad.  It means this thing is probably counterfeit: the counterfeiters found the same PDF you did because it was the first/easiest document to find. 

I am always suspicious of the bargain priced items at the big-box.  Even legit brands often "make" items specifically for one big-box store. If you have a part number that only associates with one big-box, run screaming.