Is there a way to efficiently execute ORDER BY + LIMIT using an index in Blazegraph?

Question

I am playing with Blazegraph. I insert some triples representing 'events', each of 'event' contains 3 triples and looks like this:

<%event-iri%> <http://predicates/timestamp> '2020-01-02T03:04:05.000Z'^^xsd:dateTime .
<%event-iri%> <http://predicates/a> %RANDOM_UUID% .
<%event-iri%> <http://predicates/b> %RANDOM_UUID% .

Timestamps represent consecutive moments of time, each next event is 1 minute later than the previous one.

I have 10 million 'events' (so 30 million triples) in the graph.

I run the following query:

select ?event
where {
  ?event <http://predicates/timestamp> ?timestamp .
}
order by ?timestamp
limit 15

I expect it to be executed effectively using POS index for ordering, but it looks like it attempts to do a sort of all 10 million timestamps in memory as the query takes more than 2 minutes to execute.

Adding a hint saying that a range query is safe does not help either (well, the hint is about range queries, but I decided to still try it as it seems to actually be about 'all objects of this predicate are of the same type'):

select ?event
where {
  ?event <http://predicates/timestamp> ?timestamp .
  hint:Prior hint:rangeSafe true .
}
order by ?timestamp
limit 15

Still same 2 minutes and 20 seconds.

In relational databases and MongoDB you just add an index and such queries work fast.

Is there a way to execute such a query efficiently on Blazegraph?