I agree.
Johnston moved back to the Rappahanock/Rapidan line and had eight divisions available to defend it.
Fredericksburg was under Holmes' command and then Longstreet's when Holmes was reassigned, They had the following around Fredericksburg:
Whiting's division of 3 bdes (Whiting, Hood and Hampton)
Holmes' division of 4 bdes (French, Walker*, Field and SR Anderson)
and were fortifying the heights behind Fredericksburg that cost Burnside so dear.
The other major corps was occupying the area around the O&ARR bridge across the Rapidan (having burned it and the one over the Rappahannock ISTR) and covering the fords with:
GW Smith's division (GT Anderson, Wilcox* and Toombs)
Longstreet's division of 3 bdes (AP Hill, DR Jones and Pickett, with DR Jones being senior and commanding the division in lieu of Longstreet's assuming a "corps")
Ewell's division (Elzey, Trimble and Taylor)
Early's division of 3 bdes (Early, Rodes and Kershaw)
DH Hill's new division assembled from two slack brigades (Griffith and GB Anderson)
Stuart's cavalry
On the flank is Jackson with his division.
Historically Jeff Davis was going nuts over Burnside and was pulling brigades from other stations to form an army to oppose him. He asked Joe Johnston for Longstreet and his division, but Johnston objected to losing his best division commander. Davis then had Walker and Wilcox pulled from Johnston, Cobb from Magruder and Gregg from SC to add to the NC forces.
Very quickly when McClellan started moving in April Cobb and Wilcox were ordered to Magruder and Gregg, Branch and JR Anderson from the NC force were sent to Northern Virginia where they formed "
The Army of the North" with Field's brigade at Fredericksburg and nominally with Ewell's division.
If McClellan inclines to an attack on the Rappahannock/Rapidan line one suspects, Wilcox and Walker would be recalled, and Cobb, Gregg, Branch and JR Anderson's brigades would rapidly be sent north, along with Colston's and Pryor's from Norfolk. This would give Johnston 10 divisions to defend a secure river line.
Urbanna was nixed not by Lincoln etc. directly, but by the Corps Commanders. They thought landing at Urbanna was too dangerous and exposed with Johnston behind the Rappahannock. It was them who insisted on Fort Monroe and the Peninsula, which McClellan considered the weakest option. Indeed back in January he'd asked James Shields about Yorktown, and Shields had said it would take six weeks to reduce it and move on.
Because of this I don't see there being any support for a landing on the lower Rappahannock, and it's a grind down the railroads.