Agreed. There is little to no difference in these models between 40% and 60% likelihood of winning as they are fairly sensitive to "corrections" applied to poll averages. I am quite skeptical of models that claim to predict the outcomes of singular events, like who will win tomorrow's Monday Night Football game. Statistical models of collective things, like how many US voters will vote for Donald Trump is different. Measuring errors and correcting bias in data collection are normal things.
For anyone who doesn't know, in these election models they select random samples of test elections with the percentages for each state based on the measured voter polling preferences to create a random election in each state. Half will be above the average and the "spread" will depend on the measured statistical polling margins of error. A whole bunch of "simulated elections" and then count the percentage of simulated elections that goes to each way. That is the number they report as the 60%, etc.
Where things go quite astray is that Silver has decided to model the estimated final poll numbers. Since this "Trump lead" started circulating online, I have seen several people commenting on the "model adjustments". One that apparently relevant now is the "convention bounce adjustment'. In the old days, when more people watched live TV and partisan polarization wasn't as strong, pollsters usually saw a candidate go up a few points in the polls after their convention. Usually this "bump" would go back to "normal" afterwards. Silver has built "corrections" for the "convention bump". From what I have read online, with only minor polling changes, the "model probabilities" shifted because now there is a (negative) correction for the assumed "bump" in polling from the convention (there really wasn't) and so it shifted from ~60% Harris to ~60% Trump. If there are no more changes in actual polling, it will flip back. Neither for any actual events, just because of assumed correction in a model.
I'm not saying it should really be 60% Harris, or anything, but rather that these models are generally problematic and full of assumptions masquerading as "scientific statistical models". Track the polling averages if you like, but if professional campaign managers are "panicking" about a shift in Nate Silver's model (they aren't) they are truly incompetent.