Moving WSBA to 860 in the fifties would have been a serious trade-off. Yes, it would have improved the day coverage at least somewhat, but at the expense of any nighttime coverage at all, since 860 was (and still is) a Canadian clear channel.
By 1953, there were already daytimers on 860 in Pittsburgh (WHOD, the future WAMO) and in Philadelphia (WTEL, which had taken the tradeoff and moved to daytime-only operation on 860 from a share-time with WHAT on 1340), and neither had much in the way of power - each was then just 250 watts. WAYE in Baltimore came along a year or two later, also a daytimer.
The Pittsburgh and Baltimore stations would eventually get night service when the rules were relaxed in the 90s, but not any significant power: 66 watts in Baltimore, 830 in Pittsburgh.
Even if WSBA on 860 had been able to crank up day power to 10 kW with a directional array, it still would have ended up with a signal not much better than what it had on 910.
(I suppose it's possible that the channel WSBA could have gone to was 850, where WJAC in Johnstown eventually ended up with 10 kW day and night, but that came with compromises, too: a nine-tower directional array that required a lot of land and a lot of work to keep in tune. And a move to 850 seems a bit unlikely, since WEEU in Reading was already on the frequency at that point.)
I should note, also, that in my travels as a radio historian I've heard a lot of "the FCC offered WXXX a chance to go to 50 kilowatts but they turned it down" stories, and that many of them, if not most, have turned out to be apocryphal.