@Jdforrester-WMF reported this as a bug with `upright` support, but I think the bug is more general. It just so happens that `[[File:Foo.jpg|thumb|upright=0.5]]` is a special case of this:
```
$ echo '[[File:Foobar.jpg]]' | tests/parse.js --prefix enwiki | sed -e 's/height="28" width="240"/height="200" width="200"/' | tests/parse.js --prefix enwiki --html2wt
[[File:Foobar.jpg]]
$ echo '[[File:Foobar.jpg|thumb|upright=1]]' | tests/parse.js --prefix enwiki | sed -e 's/height="26" width="220"/height="200" width="200"/' | tests/parse.js --prefix enwiki --html2wt
[[File:Foobar.jpg|thumb]]
```
But this works:
```
$ echo '[[File:Foobar.jpg|240px]]' | tests/parse.js --prefix enwiki | sed -e 's/height="28" width="240"/height="200" width="200"/' | tests/parse.js --prefix enwiki --html2wt
[[File:Foobar.jpg|200x200px]]
```