Market Efficiency

Dear sir I’m having a bit of problem with this bpp mock exam mcq:

Shares prices quoted on astock exchange are observed to reflect historical share price information and other historical information about a company, but also responds immediately to other information about the company when it becomes publicly available. In recent years share prices have been unpredictable and volatile.
which market efficiency is this:
1)weak form
2) semi strong
3)strong
4)not efficient

My answer: I ticked weak form, because its the historical information being reflected in prices.

Their answer: semi strong form.
their explanation:new information that effects share prices may arrive in an unpredicatble way(random walk theory) so share prices dont follow a set pattern and may move in an unpredictable and volatile manner.

my problem: Isn’t random walk theory a characteristic of weak form efficiency? Why are they calling it semi strong form?

Thankyou