The increments are accelerating, not the growth rates. The...

The increments are accelerating, not the growth rates. The growth rates themselves will always enter deceleration in short time because the base gets larger too quickly. However the increments from $1.5m ACV in the US at the start of the year - plus another $1.6m in the first half, plus another $2.2m in the second half - the increments are accelerating, there is no doubt.

But yes as the base of the year on year revenue gets larger, the growth rate itself appears to shrink. If the rate doesn't shrink then the growth is exponential - but exponential growth is just not possible for a sustained length of time.

Same as a savings account with regular deposit amounts. The second month the balance grows by 100%, but after 10 months its only growing at 10%. After enough years the growth in balance slows towards the interest rate. However the amount added to the account each month forever gets larger and larger, in spite of forever shrinking growth rates.