If a brand decides to release a budget version of their expensive product with a value-for-money proposition ... that is not shrinkflation IMO. (whether that value-for-money proposition is mere marketing hype or well received and is closer to reality ... is secondary)

If seemingly the "same" product -- in this example say 'MacBook Pro' base model for current year -- delivers less goodness, less value compared to its price year-on-year. If the price appears to stay more or less the same but the product is made weaker in service of higher margins for the seller. THAT would typically qualify as shrinkflation ... in my understanding.

This is more objectively measurable in comsumer goods where you can see the packaging being tinkered with over time so consumer thinks they are getting the same SKU but this year's packaging has less of the product tghan last year's, at similar price point so it doesnt register as price inflation.