I couldn't read the paywalled article, but yes. My auntie was born to English parents in the UK, moved from UK to Switzerland when she was in her early 20s and

I couldn't read the paywalled article, but yes. My auntie was born to English parents in the UK, moved from UK to Switzerland when she was in her early 20s and only visited the UK a handful of times after that. I never met her until she was in her mid 70s when she visited the UK for her mum's 100th birthday, and she really struggled with English even though it was her mother tongue. After 50 years of rarely speaking the language, she'd stopped thinking in English, and although she could recollect most vocabulary (although not as quickly as German), she could only construct English sentences by thinking in German and translating that to English, and usually ending up with German word order.