Thanks for everyone's input. I might reconsider my original stance on the issue and allow a combination with restrictions. At least y'all have given me a couple more arguments to contemplate.
Second, the feat, as written, does not support charge used with Spring Attack, because Charge is NOT "the attack action." Not that it should keep you from combining charge with Spring Attack, since the Sage did say it was allowed.
Well...Charge is an attack action according to the table on page 122 of the PHB. So even that is a bit ambiguous.
Beware of overly literal interpretations of the rules. Using the strictest interpretation of the wording, one could not use Spring Attack barehanded - but I have yet to come across anyone suggesting that is the case.
It's my understanding that a charge could be combined with Spring Attack for the purpose of avoiding reach AoOs, but you certainly couldn't move after the charge (though DMs could allow this as a hosue rule).