Form is now using this code to automatically set FormField/Multiline when containsOne - containsMany are used.
if ($f->type === 'array') {
$limit = ($f->reference instanceof ContainsMany) ? 0 : 1;
$model = $f->reference->refModel();
$fallback_seed = ['MultiLine', 'model' => $model, 'rowLimit' => $limit, 'caption' => $model->getModelCaption()];
}
However, ContainsMany::getDefaultPersistence($model) in atk4/data throws exceptions: 'model should be loaded.'