mmm tail emission is constant emission as "constant value", like "n fixed bitcoin every block". And it represent a decreising percentage-inflation cause the inflation/supply ratio is something like n/[n(b)] where n is fixed and b is growing number of blocks. So inflation is going asimptotically to zero, with different speed depends on how the tail emission is designed.
Yeah, I agree that constant-percentage emission, like "1 % of supply every year", is a form of ever growing inflation "in value" and it bring bad incentives and time-preferencies.