GroupByParam on Taxonomy template

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

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

However, I get this error:

error calling GroupByParam: there is no such a param

whereas the following:

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

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

Doug Webber[Seminars]
Alyssa Battistoni[Seminars]
etc

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.
tags:
  - Doug Webber
  - JFI
  - Jain Family Institute
  - Higher Education
  - Research
  - Accountability
  - Student loans
types: ["Events"]
events: ["Seminars"]
---