it's not an intentional update, it's highly experimental and only exists to have the community help them find bugs. it will be fixed, if you get annoyed by this, wait until the final release comes out, it will not have these bugs.
there is no iron golem spawn egg anyways, you'd never get it even in regular form.
This is its intended behavior, use a repeater to extend the pulse and a comparator to keep it indefinitely.