You can look at the deal as a fan does.
Or you can look at the deal as a businessman and an agent as do the Rams and Goff's very wise agency.
The Rams needed to get Goff signed and sealed for as long as possible before the craziness of more mega deals for Prescott and Mahomes start getting serious. By doing this they get the best possible value.
Goff's agent needed to get Goff signed to guarantee his future at current peak earning value as soon as possible. The issues for a businessman and agent are value, risk, and total compensation over a given period of time.
Vinny is looking at it as a businessman and an agent would. He's not thinking in terms of taking that portion of a contract that starts 2 years from now and dividing the total compensation by 4. Any nerd can do that.
The net effect is that this is a 6 year deal regardless of the way it was technically structured so as to NOT be labeled as a 6 year deal. The Rams have, as of yesterday, locked up their guy for 6 more years, based on today's market value, but also don't take any salary cap hits above what they otherwise would have for the next couple of years. Since the contract is an extension whereby the new agreement INCLUDES the understanding that the pay Goff would otherwise have received from his rookie contract remains the same, then it makes sense from a businessman and agent perspective to take the compensation from those 6 years and divide by 6 when it comes to value, risk, and total compensation.