Originally Posted by CPMaverick

There used to be separate ETA visas for business visitor and tourist activities. This is no longer the case.

Since March 2013 both tourist and business visitor visas are now exactly the same, subclass 601. ETA 601 "Allows a person to visit Australia as a tourist or to carry out business visitor activities such as making general business or employment enquiries, negotiations or participating in a conference."

"What an Electronic Travel Authority lets you do >> Your ETA lets you enter Australia for up to three months at a time as a tourist or for business visitor purposes."
https://www.homeaffairs.gov.au/trav/visa-1/601-

Because the tourist visa and business visitor visas are one and the same, there is no issue whatsoever entering as a tourist if you selected your ETA purpose as 'business' when you applied. I believe this question is only used for tracking/survey purposes. Either way the visa you receive is valid for business (in the way business is defined in the terms) or tourism.

*Note that I am not a lawyer and this is not legal advice.