Perhaps on the efficiency side. On the performance side it would be true even on a small site (unless it was all static, cached content).
Twitter is a one-in-a-thousand company with traffic amounts that most of us here will dream of ever achieving.
And not every low-traffic site is simple CRUD. If you do image processing, applying machine learning, natural language processing (or a thousand other things that are CPU intensive), it's nice that you can directly use one of the many high-performance libraries available in the Central Repository in your webservice.
Even writing you frontend in Java first would (most likely) not have helped you coping with the new-found challenges in that heights.