This can't possibly fix anything. Presumably you meant After, not Wants. I'd still be suspicious because there's nothing short of a custom written unit which will provide network-online.target.

If you're right, then I do not understand why adding that line works for me.
After your comment, I did some digging and found this:

man systemd.special(7)

network-online.target
Units that strictly require a configured network connection should pull in network-online.target (via a Wants= type dependency) and order themselves after it. This target unit is intended to pull in a service that delays further execution until the network is sufficiently set up. What precisely this requires is left to the implementation of the network managing service.

Note the distinction between this unit and network.target. This unit is an active unit (i.e. pulled in by the consumer rather than the provider of this functionality) and pulls in a service which possibly adds substantial delays to further execution. In contrast, network.target is a passive unit (i.e. pulled in by the provider of the functionality, rather than the consumer) that usually does not delay execution much. Usually, network.target is part of the boot of most systems, while network-online.target is not, except when at least one unit requires it. Also see Running Services After the Network is up for more information.

All mount units for remote network file systems automatically pull in this unit, and order themselves after it. Note that networking daemons that simply provide functionality to other hosts generally do not need to pull this in.

Yes the key here is the last sentence of the first paragraph: "What precisely this requires is left to the implementation of the network managing service."

network-manager-online.service seems to pull in network-online.target. So, users of network-manager will benefit from this (probably no one else).

A better solution would be to file a bug upstream for polipo to implement support for dynamic binding.