Baby dolphins cannot be spawned randomly through spawn eggs

The Bug

Baby dolphins cannot be spawned randomly from spawn eggs, unlike other mobs that have baby variants, and even squids and glow squids, whose baby variants were added in the same snapshot as baby dolphins (24w33a).

Steps to Reproduce

1. Turn on hitboxes using F3+B to see if any baby dolphins spawn.
2. Summon many dolphins using dolphin spawn eggs, being careful to not accidentally right-click on an existing one.
3. Go above the dolphins and look at all of them carefully.

Observed Results

There are no baby dolphins that were spawned from the spawn eggs.

Expected Results

Baby dolphins would be able to randomly spawn from dolphin spawn eggs.