Assertion:
The DIR="RTL" attribute right aligns the content of INPUT elements WITHIN the form field, not the element itself relative to the viewport as it does for other elements.

Plain Input Type=Button field, value="button":
filler text filler text

Input Type=Button field, value="button", Dir=rtl:
filler text filler text

Plain Input Type=Button field, value="This is a longer Button value example":
filler text filler text

Plain Input Type=Button field, value="This is a longer Button value example", Dir=rtl:
filler text filler text