This blog post includes notice for the Cambridge grammar, but also an interview with Siebenthal about the English edition of his grammar:
From the linked blog:
There is no doubt that 2019 will be known for decades as the “Year of Greek Grammars” in the English-speaking world.
2019 will be remembered for many things – most of them disastrous – but I’m quite certain it won’t be known for decades as the “Year of the Greek Grammars” in the English-speaking world or anywhere else.
Seriously? Lighten up Hy. I think the writer is being just a bit facetious in talking to people who have a serious interest in Greek grammars. For my family, 2019 will be remembered as “The Year Our Now 18 Year old Schnauzer Lived Another Year.” It’s a contextual thing… 
Oh, I love you guys! Just moved a post to this part of the forum and discovered this thread in the process! I had completely missed Siebenthals grammar and that Porter hade edited Moulton anew! Awesome! 