I suspect the key phrase in the quoted article is what I've highlighted below:
The Cardinals are looking to trade multiple outfielders given their logjam of upper-level talent, writes Derrick Goold of the St. Louis Post-Dispatch. The Phillies...have had interest in some of the Cardsâ outfielders in the past, Goold notes...
I went to the original article in the St. Louis Post-Dispatch, and it appears that the MLBTR writer's paraphrase is a bit stronger than Goold's original words:
Cardinals general manager Michael Girsch said the team intends to move some outfielders this winter and has started getting a sense of the teams that have âtrue interest.â Girsch declined to discuss specifics. The San Francisco Giants are in need of an outfielder, and the Cardinals have had discussions with them.
The Phillies and Baltimore Orioles are also teams that have had had at least passing interest in at least one of the Cardinalsâ outfielders. Randal Grichuk has been the outfielder that comes up the most often, and he was scouted at the trade deadline by a handful of teams.
Your observation about Grichuk is on the money. HIs OPS+ in 2017 was 95; Altherr's was 124, Williams' was 113, Herrera's was 104. If any of those three were a poor defensive outfielder, one might talk about Grichuk's defense - but all three Phils outfielders are defensively sound (any of them could play CF, two of them have right field arms). Grichuk is not only not an upgrade, it looks like he'd be a downgrade. He is younger than Altherr (seven months younger!), but older than Williams and Herrera. This would make no sense at all.
But... Grichuk is RH! Swapping him for one of our LH outfielders...err, no, we're not overly LH (Herrera, Williams, Crawford) either. That argument won't fly.
Irrational... and probably nothing there at all, just a St. Louis sportswriter speculating, because the Cardinals have an outfield glut. I can't imagine what the Phils could trade to St. Louis that would satisfy what Goold describes as the Cardinals' objective:
the Cardinals remain a team looking to flip multiple outfielders for one significant, substantial, lineup-reshaping addition.
So, we trade...What? Hoskins? Crawford? - for multiple outfielders we don't need? Nah; nothing here.