Potential Employer Requesting Historical Base/Bonus Over 3 Year Period - Is This Normal?

I’m interviewing with a boutique firm (consulting & corporate advisory) and the Partner is requesting my historical compensation information (including pay slips) for the past three years as part of their interview process.

They used the language "we are required to collect your historical base/bonus amounts over the last three years."

For context, we hadn't discussed remuneration expectations yet, and I'd already undergoing a capability assessment and providing references.

I'm concerned about this request for several reasons:

(1) Early Timing: Asking for salary history before discussing expectations is unusual and potentially disadvantages candidates. Employers often use past earnings to anchor offers below market value, regardless of their qualifications.

(2) Transparency and Pressure: This statement suggests that if I do not comply, it will be a dealbreaker for their interview process noting it’s not a legal requirement in Australia.

(3) Data Scope: Three years of detailed pay slips seems excessive and unnecessary.

While I'm interested in this opportunity, I'm hesitant to share this information due to the concerns above. It feels invasive, and I'm worried it will significantly impact my offer to the downside.

Is this normal? If not, any advice to share?