I visited in 2017. The guides were asked questions about the risks of eruptions and how come visits are permitted. The reply was something along the lines of volcano activity is monitored and visits would be suspended if certain warning signs increased.
I don't remember exactly but there was also some sort of evacuation procedure mentioned - not sure how effective this would have been though...
Not sure how anyone who hasn't studied geology would be adequately informed to judge the risk.
From the linked SMH article (note, written by a Kiwi and aimed at Kiwis):
One report suggested that more emphasis was placed on the risk of seasickness than on the possibility of fatal burns and damage to internal organs from toxic gas and ash.
Does it not make more sense to inform visitors of a tangible risk that actually has a chance of affecting them such as seasickness (on my visit, the wake from a passing boat did make ours severely rocky for a few minutes) rather than a theoretical risk - that is to say if fatal burns and organ damage are actually likely to happen, the trip shouldn't be going ahead... which we now know with hindsight