No,
it says he "...arrived on the battle-ground in front of Keedysville about 9 o'clock a.m...", i.e. beyond Keedysville near McClellan. It goes further to say "...and subsequently led the advance of Franklin's corps to support the right wing...", showing that there was no further marching. It had indeed arrived at the battle-field. It was rapidly sent to reinforce Sumner, because as McClellan's 0910 notes, he feared the right was suffering.
The Sumner order fits what is known:
“General McClellan desires you to be very careful how you advance, as he fears our right is suffering….P.S. General Mansfield is killed and Hooker wounded in the foot.”
Mansfield was killed around 0800 and Hooker was wounded around 0830. The news of the loss of two corps commanders would have been fresh in McClellan's mind at 0910.
You are trying to shift the arrival time because there are two different 0910 timestamped orders in the OR, both of which describe different situations, and so one is incorrectly timestamped. The incorrectly timestamped one, in light of the arrival of Smith's division at 0900 (and it going into action at 1000), and the suffering on the right vs the successes at 0800 has to be the Burnside order. It must be an earlier order.
No, the Burnside order says Franklin's corps was approaching, and 1.5 miles away. A curious thing to say when the corps had in fact arrived. He also said "So far all is going well", which is at odds with the loss of two corps commanders and a rebel counterattack that hat pushed the right back.
It must be the Burnside order that is mislabelled.
You are confused.
The Burnside order mis-labelled as 0910. Franklin's corps, or the advance of it, arrived ca. 0900. When he ordered Burnside in, it was 1.5 miles away, say 45 minutes or an hours march. That would be consistent with this being the 0800 order that is mis-timed.
McClellan said he sent an order at 0800, and the man how carried it, Lt Wilson, recorded it in his diary.
McClellan then says after an aide confirmed nothing was happening he reissued the order. That could account for the wrong timestamp - the 0800 was simply recopied and sent again.
That same aide came back with news that Burnside didn't move on receipt, and so McClellan sent Col Sackett to ride Burnside. Sackett confirms this, and confirmed he remained there, as ordered, under 9th Corps was up the hill. He returned to McClellan's CP at 1600, but McClellan was with Sumner on the right. He also observed Col Key's two visits to Burnside.
The timings in reports are:
Burnside (9th Corps): claimed he didn't receive an attack order until 1000
Cox (9th Corps): says he received the attack order at 0900
Gerhardt (46th NY): Received order at 0900
Ferrero (Brigade): Say he advanced, on orders, at 0900
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Benning (commanding the defending brigade): Says the Federals approached at 0800 and drove in his skirmishers at 0900
Toombs (commanding division): Says the first attack was between 0900 and 1000.
Capt
Lewis (commanding 2nd Georgia): Says he was attacked at 0900
We can discount Burnside's claim, because he did attack before 1000.
McClellan may have repeated Burnside's claim in his first AAR, but it is clear from his writings that he didn't believe him, and was trying to mollify Burnside.