Should "universal pedals" be avoided?
In context of the low cost pedals, you need to look at the user and how they ride. Would I trust them on a trials bike or downhill MTB?, no, but then I would not trust a cheap pedals with a one piece axle.  Would I trust them in a situation I would trust a similar pair of cheap one piece axles, absolutely.  

In theory the two piece axle will be less reliable as it has another failure mode that does not exist on a one piece axle. However, the failure of the extra threaded join is probably much less likely than the pedal to crank join, due the thread locker. Therefore, the increased risk is marginal. 

So the question is not 'should they be avoided because they have a two piece axle", its "Should cheap pedals be avoided"