What value do you want to show on axe Y if within actual time bucket you have more than 1 value.
this is why avg/max/min is the choice.
If you use all three and choose buckets minimum interval to the granularity of your dataset , all 3 max/min/avg will have the same value so in this case you will have you graph.
however in case of many records Kibana automatically scales up the interval .. To see all values you shoud zoom-in.
in time series data you have allways data (per interval) so you have to do some aggregation within this interval.
