LW have added some warnings, but they are not necessarily obvious to everyone. Especially since many people will not know whether they have 64-bit machines or not. Only the mac intel machines released past couple of years & perhaps the macbooks over past 12 months (not sure about macbooks.)
I've squashed the image sample below up a little to show the pro purchase page warning.
But if I may say, at present you are not losing anything by not being able to use LW 5. Only thing you miss out upon is the
Friends option. LW 4 has many more tools than LW 5. It will probably not be until end of year before LW 5 re-introduces the tools that LW 4 has. And that's only via pressure some of us have been putting upon the Developers. lol
LW wanted to simplify the program, but in its present state is far too simplistic, so much so that even
many new Windows users have been downgrading to LW 4.
LW 5 has been getting the thumbs down from probably the majority of users.