Diesel oil is still very much available in gallons, Rotella & Delo mostly, the next size is 2.5 gallons. Most heavy duty engines you're talking gallons and not quarts so the market for the HDEO hasn't changed to the 5 qt jugs. You can find dual rated Euro oil in 5 qts but it's not HDEO.
That oil was most likely sometime during the 90s. We have some older Rotella jugs still around and none of them have the XLA, the ones we have just say triple protection before it was branded as t4 and previous to the t5 & t6 which weren't even out yet.