W. H. Griffith Thomas wrote the book, The Pentateuch: A Chapter by Chapter Study published by Kregel.
Did W. H. Griffith Thomas write this when he was still reformed, before he moved toward dispensationalism?
I can't find that it is anything but a posthumous work. Possibly it is a collection gathered from the author's notes, including sermon notes. If it is as late as it seems, I would not think it had a "stamp" of one period in his life.
I would expect it to have at least a tinge of dispensationalism; although I don't recall a particularly noticeable effect in his "devotional commentary" of Genesis.
On the other hand, I did not find WHGT's treatment of Genesis especially rewarding. It contained very little insight for my use in preaching; although for some I suppose it is a goldmine. It is heavy on the borrowing of the OT for a moral lesson in life.
The previews of the subject of your inquiry (which can be found via the internet) give a quite different presentation (an overview) of the Pentateuch. It looks like more of a content-digest. However, still there is with each ch. a surface level "how to use this passage" that strikes me in most cases as tediously moralistic.