The Old syntax was:
/spreadplayers <x> <z> <spreadDistance> <maxRange> <respectTeams true|false> <player ...>

The New syntax is:
/spreadplayers <center> <spreadDistance> <maxRange> <respectTeams> <targets>

Note that in the old version you can specify multiple selectors/players.
In the new version you can only specify one selector. This might be intended, but this might make certain old commands break or more complex to achieve.

It would be nice if this behaviour could be pertained, or if selectors could be grouped in a list such as ["Dinnerbone","Jeb_","@e[type=villager]"]
Which could then be used as a single selector containing all villagers and Jeb and Dinnerbone.

In any case, wanted to point it out as a bug, since it may not have been intentional to remove such functionality.