IMCE doesn't respect site's error reporting setting

An error occur when I clicked on a plus sign in the file browser at user/1/imce while I had the Devel and Theme Developer modules enabled.

The site is set at admin/settings/error-reporting to "Write errors to the log."

Nevertheless, IMCE displayed the following error message to the browser (path to site redacted):

An error occurred. 
/[path-to-site]/imce?jsop=navigate&dir=events/images
{ "data": { "files": "\x3cspan id=\"thmr_1\" class=\"thmr_call\"\x3e\n \n\x3ctable id=\"file-list\" class=\"files\"\x3e\x3ctbody\x3e \x3ctr id=\"49ers-Express-Routes.gif\"\x3e\n \x3ctd class=\"name\"\x3e49ers-Express-Routes.gif\x3c/td\x3e\n \x3ctd class=\"size\" id=\"26084\"\x3e25.47 KB\x3c/td\x3e\n \x3ctd class=\"width\"\x3e441\x3c/td\x3e\n \x3ctd class=\"height\"\x3e553\x3c/td\x3e\n \x3ctd class=\"date\" id=\"1329170587\"\x3e02/13/2012 - 2:03pm\x3c/td\x3e\n \x3c/tr\x3e\x3c/tbody\x3e\x3c/table\x3e\x3c/span\x3e\n\n", "dirsize": "25.47 KB", "subdirectories": [ ], "perm": { "subnav": 1, "browse": 1, "upload": 1, "thumb": 1, "delete": 1, "resize": 1 } }, "messages": [ ] }<span id="thmr_2" class="thmr_call">
<table class="sticky-enabled">
<thead><tr><th>Duration (ms)</th><th>Template/Function</th><th>Candidate template files or function names</th> </tr></thead>
<tbody>
<tr class="odd"><td>1.54</td><td><div id="devel_theme_log_link_thmr_1" class="devel_theme_log_link"></div>
imce_file_list</td><td><strong>sites/all/modules/imce/tpl/imce-file-list.tpl.php</strong></td> </tr>
</tbody>
</table>
</span>

I would expect this type of error (as opposed to a "You're not allowed to do that" error) to only be written to the error log, not to the browser.