You seem to have a trouble with reading what is actually written.
Terrorism related legislation and offences cover stuff that might not always be Terrorism.
The police have said it isn't terror related. Presumbly because they cant at this stage establish a link with a terrorist group or idealogy as the motivation behind the attack.
Unless you work in a lab and its part of your job, there is no lawful reason why anyone should produce or possess ricin.
But if someone is producing it out of morbid curiosity or they want it to poison their neighbour and isn't politically motivated, then it isn't strictly terrorism.
The same applies to downloading materials that can be used to make bombs.
Terrorism link or lack of doesn’t make what the disturbed man did any more or less evil.
It was a monstrous attack and my utmost sympathy is with all the families and survivors.