Your confusion is simply the result of a misunderstanding of the present perfect continuous tense. It’s true that this tense must be used with the present participle of the verb, which of course ends in “-ing,” as in “She has been singing the blues all day.” But “has been described,” the verb of the subordinate clause in the following sentence that you presented, isn’t in the present perfect continuous but in the passive form of the present perfect instead:
“Vreken, who has been described by family members as a man who approached life with a positive attitude, was killed on Saturday while out on his morning jog.”
The passive form of the present perfect is of the form “has been + past participle of the verb” (in this case “has been described”) in contrast to the passive form of the present perfect continuous, “has been + present participle of the verb” (as in the hypothetical sentence “Vreken’s family members have been describing him as a man who approached life with a positive attitude, but their neighbors knew that this wasn’t true at all.”). You can therefore see that it is the present perfect continuous that uses the “-ing” ending for its main verb (the present participle form); the present perfect, on the other hand, uses the “-ed” ending for its main verb (the past participle form).
In the sentence you presented, the passive present perfect form “has been described” indicates that the action of describing Vreken has already been perfected or completed. In contrast, in the hypothetical sentence I provided above, the passive present perfect continuous form “has been describing” indicates that that the action of describing Vreken started sometime in the recent past, continues up to the present, and may continue in the foreseeable future.
I hope this clarifies the difference between the present perfect tense and the present perfect continuous tense for you.