You need to understand the difference between the SPP and the...

You need to understand the difference between the SPP and the placement. Under the SPP, $5000 is the maximum allowed by law without the issue of a full prospectus. The company doesn't have a choice on the amount.
The Placement is limited to "sophisticated investors" which if you check the definition, requires assets of at least $2.5m or an annual income exceeding $250K.
It's not a matter of giving larger investors preference. It's playing by the rules.