GroupByParam on Taxonomy template

I’m trying to group the pages in a taxonomy template by a Param like this:

      {{ range .Pages.GroupByParam "events" }}
        <li>{{.Title}}{{ .Param "events"}} </li>

However, I get this error:

error calling GroupByParam: there is no such a param

whereas the following:

  {{ range .Pages }}
    <li>{{.Title}}{{ .Param "events"}} </li>

successfully returns all of the pages, with their Titles, and the assigned events Param:

Doug Webber[Seminars]
Alyssa Battistoni[Seminars]

which, makes this confusing since there actually “is such a param”, the frontmatter looks like:

title: Doug Webber
date: 2019-11-22T21:40:39.248Z
subtitle: >-
  Doug Webber, Associate Professor of Economics at Temple University, joined us
  for a JFI Research Session to share the results of his recent work.
  - Doug Webber
  - JFI
  - Jain Family Institute
  - Higher Education
  - Research
  - Accountability
  - Student loans
types: ["Events"]
events: ["Seminars"]