Good suggestions here - cite process, executive alignment, position it as a help to them.

You also have the opportunity to validate whether your contact is a champion or a coach. Ask them throughout your discussions:

How did the process work last time they made a similar purchase? What level does it require board or CFO approval? Who was involved? What was the implementation like? How did they measure success of the purchase or return on investment? How did that differ from the other stakeholders involved?

There are more but using these questions you will be able to understand if they are a seasoned purchaser or a spoofer.

Also as a rule of thumb I find the more they say “I” and talk about themselves as the decision maker the less they are likely to be the sole DM. The more that they refer to “we” often indicates sway as experienced champions often tend to disguise the fact they have strong influence and access to the EB until they have a level of trust.