So I'm aware that transcription into Japanese is not always clear-cut, and there are plenty of exceptions. It sort of makes sense that "Australia" is オーストラリア not *オーストレリア and "stadium" is スタジアム not *ステージアム, perhaps because those are partial transliteration, not pure transcription. But why is "studio" スタジオ? Shouldn't it be at least be something like *ストジオ? Or are dictionaries wrong about its actual etymology (i.e. from English)?
tu in some words is rendered as タ. As far as I can remember now, ト is not used.
- bathtub バスタブ
- study スタディー
- tuck タック
- tumbler タンブラー
In addition, etymology of studio is the same as that of study (from Lantin studium). To my ears, ストジオ and スタジオ are equally bad as the phonetic approximation of studio, but somehow スタジオ is at least understandable for those who already know the facts above. スツジオ might have been another possible option (two /tu/ is ツー, tool /tuːl/ is ツール), but I find it hard to pronounce.
Most people today understand the sounds /tu/ and /di/ that appear in loanwords (See: What "non-standard" katakana are commonly used?), but these were not available in the past. Had this word been introduced firstly in the 21 century, it would have been ストゥディオ.