If he's taper crimping I assume the OP is using a Lee set with a FCD.
This is my take - loading manuals recommend crimping loads for semi-auto actions because it's the safest way, and it's the same reason all factory ammo is crimped. The casual reloader may not pay a lot of attention to neck tension, or even know whether it's good enough on the cases they're loading. Crimping adds insurance against a bullet getting pushed back into the case and possibly raising pressure to a dangerous level. When making a recommendation to a relatively new reloader or to someone who's proficiency I don't know, I'd also recommend the safest method. Personally, I don't crimp every round I load for a semi-auto rifle but when I'm using a bullet with a cannelure I usually do - because I haven't found a reason not to.
Pretty much all rifle seating dies make a roll crimp rather than a taper crimp. The extra Lee FCD is the only exception I'm aware of, but the standard for rifle dies is a roll crimp. That's likely why you saw that recommendation. If the bullet has a cannelure - and if you're going to crimp it - I believe a properly applied roll crimp is probably more secure than a taper crimp.