slow scrolling back from hydra

[Zoybean]

Scrolling backwards from a hydra scrolls significantly less than expected (about half a page less). Calling the same commands from bare keybinds is unaffected.

minimal init.el

(defvar bootstrap-version)
(let ((bootstrap-file
       (expand-file-name
        "straight/repos/straight.el/bootstrap.el"
        (or (bound-and-true-p straight-base-dir)
            user-emacs-directory)))
      (bootstrap-version 7))
  (unless (file-exists-p bootstrap-file)
    (with-current-buffer
        (url-retrieve-synchronously
         "https://raw.githubusercontent.com/radian-software/straight.el/develop/install.el"
         'silent 'inhibit-cookies)
      (goto-char (point-max))
      (eval-print-last-sexp)))
  (load bootstrap-file nil 'nomessage))

(straight-use-package 'hydra)
(require 'view)

(defhydra hydra-view ()
  ("u" View-scroll-half-page-backward "View back")
  ("U" View-scroll-page-backward "View back"))

(keymap-set global-map "C-c v" 'hydra-view/body)
(keymap-set global-map "C-c u" 'View-scroll-page-backward)

What I tried:

1. fill a buffer with a few screens of text, and scroll to the end.
2. call View-scroll-half-page-backward from a hydra (C-c u u u)
3. call View-scroll-page-backward from a hydra (C-c v U U U)
4. call View-scroll-page-backward directly (C-c U)

What I expected to happen:

1. at the end of a large buffer
2. view scrolls back half a screenful at a time
3. view scrolls back 1 screenful at a time
4. view scrolls back 1 screenful at a time

What actually happened:

1. at the end of a large buffer
2. view scrolls back a few lines at a time, or not at all
3. view scrolls back half a screenful at a time
4. view scrolls back 1 screenful at a time

Other notes:
It's not just view that's affected. I tried my own versions based on scroll-down and they also exhibit the same behaviour when called from a hydra.

(defun scroll-half-page-down-command ()
  "scroll down half the page"
  (interactive)
  (scroll-down-command (/ (window-body-height) 2)))

(defun scroll-half-page-down ()
  "scroll down half the page"
  (interactive)
  (scroll-down (/ (window-body-height) 2)))

Scrolling forward appears unaffected.