Hi themaccabee,
both of the figures you have shown to us don't tell us the truth - that means they are not compatible with the information of the referenced document.
(No voltage source with source resistance of zero and no sigle ended operation).
In the document, there is an ac line to be filtered. That's a different story - and in this case (line filter principles), of course, you can place a shunt capacitor in front of the inductor to design a second order system.
Added after 1 hours 12 minutes:
Hi themaccabee,
did you realize that in Fig. 4 of the referenced document the input is a the RIGHT side ?