Jein (Yes and no). Helmut Schmidt even advocated for diversification in 1988 (no importer should account for more than 30% - of course more with oil in mind but the principle stands).

https://www.zeit.de/1988/08/sieben-prinzipien-vernuenftiger-...

Contrary to this, Russian gas imports to Germany used to account for 40% of total consumption in 2012 vs 52% as of today.