It’s not clear to me that he indicated anything other than that they were ‘asleep”.
This is further evidenced by a complete dearth of mention that there was anything to be gained by prayer to the deceased in the Epistles of Paul.
Surely he would have exhorted Believers to do so, were there spiritual benefits to be derived...
You all can do as you wish; I don’t pray to the dead.
Or, surely he would not have bothered to mention it, if it was something they all took for granted.