Don't confuse those that are permanently disabled (multiplication, division, bitwise operations, string operations) with those that are not relayed (flow operations, stack operations, addition, subtraction, crypto functions).
I understand the difference.
They should have temporarily disabled them. For example, they could have disabled them for 50000 blocks (1 year). That would give them time to test for any bugs. They could extend the deadline via a soft fork later.
Yeah, I don't get why they permanently disabled multiplication. The explanation says it's because of possible bugs, but come on, it'd be pretty hard to fuck up a simple multiplication.
Disabling them was zero risk.