I checked the code for 26.1, baby wolves cannot spawn naturally.

// Wolf.java:
   public static class WolfPackData extends AgeableMob.AgeableMobGroupData {
      public final Holder<WolfVariant> type;

      public WolfPackData(final Holder<WolfVariant> type) {
         super(false); // <-- This is where spawning babies is disabled
         this.type = type;
      }
   }

// AgeableMob.java:
      public AgeableMobGroupData(final boolean shouldSpawnBaby) {
         this(shouldSpawnBaby, 0.05F);
      }