A small update:
In the end most of the big social media registered... Notable non-registered sites/companies/app included Bing, Steam, Yahoo, and PayPal.
Then what happened to them? Well, 2 days after the deadline the government then decided to extend the deadline to 27 July. Funnily enough there is also a press conference where a Ministry of Information representative said there will be no tolerance, threatening to block the big companies (at that time Twitter and WhatsApp was included) and basically warned Indonesia will replace them with local apps just like China