text-bottom vertical align for img tag showing up as bottom?

[Thermospore]

hello, I am working on adding some in-line mathematical figure images to a dictionary, and trying to set the vertical alignment. messing around in browser, text-bottom seems pretty good. but when I try and assign that vertical align in the structured content, it shows up as bottom instead:

structured content tag:

{"tag": "img", "path": "media/elinea001.png", "height": 1.21333, "background": false, "appearance": "monochrome", "collapsible": false, "collapsed": false, "verticalAlign": "text-bottom", "sizeUnits": "em", "title": "elinea001.png"}

I tried changing the vertical align for the first image in "more content 2" in validdict1.zip from middle to text-bottom, and the same thing happens

any ideas? thanks!