when a wheel builder tells you its not as strong as them why - there is a reason i say this as i used to build wheels for MTB race teams and they had upto cross 5 spoking man that was fun
we also because we could built snow flake wheels and radially laced wheels.
now back to why - radially laced is not nessacarrily weaker as all wheels are only as good as the components in them - hub flange/hub drilling,Rim width/Depth/wall construction, Spokes/diameter/butting/metal.
To build a strong radial wheel you need thicker plain gauge spokes, you need the hub drilled to accept the radial spokes and the rims also.
Currently on my MTB i have 32 radial laced spokes on a 22mm wide double wall rim with double butted stainless pokes of the front and the read is very trick cross 2 on the driveside and radial on the non drive side and i use these on a 7" travel downhill bike and have yet to even on the harsh terrain and a few crashed have to true them