My gut tells me that because every train (except for two) has at least one sleeping accommodation offered with with all five buckets, there are indeed five buckets in Arrow for each one on each train - but not all are seen as they've not yet been offered. As time goes on, some or most of the buckets shown in my chart as [ESTIMATED] will be eventually offered and if I care enough to perform AmSnag searches for them they'll be posted to my master copy of the chart.
But I don't anticipate all of the [ESTIMATED] buckets to be offered or at least spotted when offered. I only search for missing buckets when there's absolutely nothing else for me to do and I'm bored to tears.
Some might wonder: how can I tell which bucket is being offered if only a single bucket can be found? Just by comparison with the previous bucket chart and comparison with buckets already found for other sleepers on the same train. Estimates of the missing buckets are made knowing Coach buckets follow a roughly geometric progression and sleeper buckets follow a roughly arithmetic progression.
But the title of this thread is not the least bit misleading: the largest sleeper upcharge increases seen between Jan 2019 and now are for Roomettes on the SS which are up from 22 to 29%.
I'll end this by proclaiming each sleeping accommodation does in fact have five buckets - but not all have yet to be offered (or noticed, when offered). But anyone who thinks there are a few accommodations with only four buckets programmed into Arrow are perfectly free to think so. This is, after all, the land of the free and the home of the brave.