[sbuttgereit]

As others mentioned, space in rocket build area looks like it's to a point where any delay in getting completed test articles to test stands, means delaying construction. I suspect they weren't completely confident when they'd get FAA approval after getting into a full launch cycle and being pretty clearly rebuked (pulling of the TFR and announcement of the scrub by the FAA). So better to get it to the stands so they could move on the fronts they could... but also to be understood...

There's probably a cost/benefit calculation here, too: SN15 has been said to be bringing significant design improvements over the current design they're flying, and SN10 is of the older design. SN11 is probably ready or very close to ready for "high-bay" stacking... SN10 was waiting in the high-bay along with the first booster (BN1)leaving really no room for anything else to go in there. SN12, also of the same older design is being pro-actively scrapped right now and SN13, SN14 are also not going to happen so they get to SN15 faster. They have a test article at the launch site (SN7.2) to test a different construction material (3mm think stainless steel vs. the current 4mm). All that said and done... I'm sure they want to get SN10 in the air and would be disappointed by losing it... but they already have their sights fixed on the future it doesn't completely represent.