Totally agree, I mailed the company earlier about similar.
Seems bizarre to me that the company choose to turn down the 'upgrade' money that backers would clearly be willing to spend.
I was slightly short cash wise for the alpha, and would have gone for it if the funding closed a week later. I would pay the difference from my pledge to the alpha, but there's not a chance I'd put up another £200 on top to get there.
Sadly, this makes me feel slightly screwed as a backer.