Yeah, I don't like it. I think if you're going to let Rugby scrums happen like that you're going to need to consider other rule changes to balance that out.
For example - there is no pass play audible in Rugby. If you're going to tush push, you should have to declare it and allow the defense to adjust. Also, in Rugby, the defense can link arms in order to push back.
Right now it's heavily imbalanced, due to football rules, towards the offense. I'm not a proponent of any concept (offense or defense) standing if it has a significant imbalanced advantage.