Carbon probably only lasts a week in many tanks, after which it is basically normal filter media. Throw in a piece of tannin soaked driftwood, and it's probably saturated in a few hours.
I imagine Chemipure likely behaves much like carbon. I seem to remember using it in filters many years ago, but I don't recall any real difference between tanks in which I was using it vs. those in which I was not.
The best way I've found to reduce dissolved organics is just to change water.
Having years of experience doesn't always mean that a person knows what they are talking about, although it is certainly an indication. (I'm not in any way saying that your friend is wrong or doesn't know what he is doing.) The old farmer that my parents bought their property from used to put boards in the ground across his garden because he believed it would stop the frost from climbing up the hillside. He also planted all of their chestnut trees so close together that they were stunted and intergrown. He had 60 years of farming experience.
There are many forum members who use Purigen for what seems like the same reasons you are considering Chemi-pure. I couldn't attest to whether one is better than the other, or even whether there's much of a benefit, but I certainly don't think either one would be detrimental.
All I can tell you is that most of us on this forum aren't using Chemi-Pure, and it is not a new product. I really doubt that using the product would hurt in any way. Even if it absorbs fertilizer, it will probably be saturated in a few days with regular EI type dosing. As far as whether it keeps algae at bay I would tend to be skeptical. Algae grows just fine even with extremely low nutrient levels.