Right out of the gate you hit the issue that there simply aren't many "very early onset IBD" (impacting children under 6 years old) specialists because historically there were so few cases. We've seen well regarded IBD specialists who reflexively try to order tests and procedures that their own hospital will then refuse to even perform because they can't be done safely on young children. The IBD specialists are in general simply unfamiliar with young children because of the historical rarity.
From the VEO IBD specialists we have worked with they all report that the numbers are exploding and no one has any real idea why.
On top of that most of the more modern and effective treatments for IBD and Crohns aren't approved for young children at all and even top tier insurance will fight tooth and nail against covering them because their use in children can be considered off-label.