Is Oham useful for Biblical Hebrew the same as for today Israeli Hebrew?

Yes. It is useful for both kinds of Hebrew. Biblical Hebrew has a heavy weight within the work: most of the examples supplied for the various patterns are taken from the Bible.

Today Israeli Hebrew has also been greatly taken into account. The Rules issued by the Academy of the Hebrew Language for today Hebrew have been strictly kept everywhere, at every moment, always, without restriction.

Now, it is quite true that along the centuries biblical Hebrew has been parsed and analyzed from every side and in this respect many works are available that explain and tell on the structure and meaning of every word in the Bible. Nevertheless Oham is quite useful here too, mainly in the sense that it explains how a given pattern can, at least from a theoretical viewpoint, apply not only to a given structure but to this and this and this... structure.

Of course, this greatly enlarges the reader's mind or viewpoint.