To me T4 acknowledges that the rule is not practicable or enforceable both for technical and other reasons. The ITTF is asking for players to go with the spirit.
So basically glue with rubber cement, or WBG, or even VOC (non-speed glue) as long as it would pass the VOC test in theory. I say theory as I haven't seen a VOC tester at any English tournament for a few years, even at the nationals.
Personally, I don't think any player is using old-style speed glue. Boosters, yes, but not sg.
I don't boost but I still use an old can of VOC normal glue that I had from before the ban. I do this as I believe that WBG is harmful to the wood over the long term.
BTW, all my blades are over 30 years old.