I think what he means is that there are no harmonized interludes in the vein of, say, PoM, and that's true.
Admittedly, there aren't many. But saying none at all isn't right either.
The title track has harmonized guitars after the solos. The Wicker Man technically has some during the "oooh" part towards the end, as does Dream Of Mirrors during the second "oooh" part. Out Of The Silent Planet has a bunch of them (the end of the intro under the vocals, after the fast chorus before the vocals are repeated, during the last chorus). The middle of The Thin Line keeps adding guitars and then a bunch of solos on top, before going to the quiet part.
Yes, it is true that many of those examples either are during some kind of vocals (even if it's just an "oooh" melody) or there's overlap with vocals and not a pure intrumental section. Most instrumental breaks with melodies on the album either feature a single guitar line (sometimes backed by synths) or doubled guitars in octaves. That's something that became more and more prevalent in Steve's writing from FOTD onwards.
Personall, if I had to guess, I think they were still experimenting how to deal with three guitarists and how to integrate Bruce and Adrian into Steve's late-90s writing style. BNW has a
lot of vocals harmonies. Some of them are pretty busy and rather creative. The chorus for OOTSP for example features a distinct vocal line that doesn't just double the main vocal in thirds; it pretty much does its own thing and somewhat clashes with the main vocals. It seems they gave Bruce a bit of free rein to do some of the stuff he was doing on The Chemical Wedding, vocally, while the guitars were somewhat more reserved. Those feel like deliberate choices to me and not just a consequence of the recording style.
But yeah, I concede that as far as pure instrumental harmonized interludes are concerned there are only two parts on the album (title track and Thin Line).