Well, you can't, unless you have the text source for the dictionaries.
I can confirm the behaviour you observed even with my PB603 fw 2.0.5, for both the files you've provided here.
For the Merriam-Webster's Collegiate I had a text source and I've been able to recompile the dictionary, though.
I'm afraid at the time I tinkered a lot with the original text formatting, so it's not as clean as the one you have, but the touch keyboard it's working for me, at least. I'm confident that the voices are the same.
For the 1913 version, I've never found a source to play with, so far.
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