Yes, that's true. The Iberia management made some statements about the size of the longhaul fleet of SWISS. But I personally don't think that there are some obstacles in the partnership between Iberia and SWISS. This two airlines are NOT in a strong competitive situation on their longhaul-routes. SWISS is more Latin America-oriented, whereas SWISS maintains a well-established network to Asia, Africa and North America. So this two companies are less "substitutes" than "complements" to each other. Iberia is the market leader on routes between Europe and Latin America and SWISS is not a "danger" for Iberia's position.
But I heard sometimes members of the Iberia management comparing their longhaul-fleet with the Swiss one. And they always tell that they have a fleet matching the market demands, in contrast to SWISS!
P.S. Excuse my pure English