I'd actually agree with you. On LedgerSMB we made the decision to drop support for IE due to a lack of BUTTON support. Then IE7 came out which was still too broken and we didn't support IE. Then IE8 came out and supported buttons so we could support them again.
The tradeoff was simple: marginally greater market share at the time vs the fact that if we supported IE we would not be able to use BUTTONs to separate labels and inputs for i18n purposes. Really, there was no case to be made for IE support at that point.
So developers hsould consider the tradeoffs carefully.
You are both correct. IE always had a <button> element, however it only started working like other browsers on IE8. Before that it behaved like an <input>; you had to add "type=submit" to get it to actually submit the form.
The tradeoff was simple: marginally greater market share at the time vs the fact that if we supported IE we would not be able to use BUTTONs to separate labels and inputs for i18n purposes. Really, there was no case to be made for IE support at that point.
So developers hsould consider the tradeoffs carefully.