Did you notice that in the latest version of the Model Regulations (twenty fourth Edition (2025)) a note is added to the testing & inspection of IBCs (see Volume II – Chapter  6.5.4.4.2, p. 309)? 

Regarding the leakproofness test, this note was added: 

In the 65th UN session of the Sub-Committee of Experts on the Transportation of Dangerous Goods, the expert of Germany has submitted an alternative proposal for the conditions to be used during the periodic testing of IBCs. This document supports the  Sustainable Development goal 16.6. and was accepted, resulting in the above- mentioned note.

It is expected that this note will be also introduced in the next version of the ADR (2027)