GDP remained the same must be due to the currency depreciation to USD
Rebasing needs a lot of work that will spend many human hours, the rebasing for Indonesia case is about every 10 years. Frequent rebasing like every 5 years are not necessary to do, it will just target political score while the time spent can be used on something more productive or better not adding current workforce workload too much that can lead to healthy problem and others.
Responsible government will rebase only after 10 years. Indonesia is still using 2010 as base year until now.
More about the topic coming from Indonesian statistician
Four years ago, newspapers in India published the intriguing news that their government was likely to benefit from the changes in base year for calculating gross domestic product (GDP) data, as the change would render the fiscal deficit much lower than projected
www.thejakartapost.com
PPP is somewhat better in calculating economy comparison between countries