Hi,
When a design is done the result is the result of the whitepaper studies as well as the experience of the engineer. It could be that the guy who did this design had enough experience with this kind of design to know it would be successful. You cant measure that by looking at the data sheets.
So just because the design in questionable on paper doesnt mean it wont work in real life.
Here we have the question of the operation of the op amp with various inputs that seem to go outside it's specified range of operation. There are however general rules you can follow that help when this kind of thing happens, and it is not too severe. There are two basic rules that come into play here.
1. The PNP stages allow input operation below ground. This happens regardless of the 0v spec.
2. The input can go as low as 0.4v, and for low currents would be protected from going lower than about 0.5v or so by the ESD diodes, which can usually take some milliamps.
The question of input offset also comes into play however. If the input offset is positive on the non inverting terminal (and it probably is) then the design works every time. If it is negative however and the other input is designed so that it can not go lower than this value (which seems to be what you said earlier) then the design doesnt work at all. If it is close to the right value, then yes it might work sometimes and not other times.
But since the input offset is the last question to be answered, a simple test reveals the go or no-go of the design. After all, we just want to know for sure if the design works all the time or not, for any particular op amp we pull off the shelf of that part number.
The test is to bias the non inverting terminal slightly negative, by 5mv. If the unit still operates as it did before, then the design passes. If it fails or acts erratic, then you really do have to bias it positive and there should be no doubt about the need for this. The reason for the 5mv is because that would be the worst case for this op amp according to the data sheet plus a tiny bit more.
Now you might still question the design because it goes below the spec of 0v, but that would be somewhat normal, as long as the input current is always low (like 1ma).
It would be interesting to see the results of the -5mv bias test regardless how you intend to proceed as this would tell us if the designer was really on his toes or not.