The "general" rule for standard large SB is one spike per pb. The shorter varieties almost always double spike.
but individual plants can do their own thing.

By the way, I've never heard of oncidium types flowering from an old pb. That is really something, isn't it? good for you! How old and large is the plant??

Beautiful! I can almost smell it.

Does anybodies SB produce new PB while growing the spike? I currently have one that has about a 16" spike that I just noticed is growing at least 3 new PB with a possible 4th. Just seems strange that its putting out so much energy but its a super healthy, has 6 mature PBs with one almost 4" long, plant unlike my other Onc.

Mine (which is quite large now) always has growths in various stages of development - so yes, it grows while spikes are developing. These are extremely robust growers.

oncidiums are crazy that way.
I thought it was a pattern for them to wait until flowering is finished before resuming growth again, but quite often, these plants do both at the same time. not sure if it's the growing condition, plant habit, or both.

Mine is growing roots on the new SB and two tiny little SB on this same growth. I hope the pseudobulb will form soon. Leaves on this new growth are as big if not bigger than those from the old pseudobulb. This new groth is growing at the rim of the pot so the two new tiny growths it's starting to develop will grow out of the pot if they grow. Should i repot it to the other side of the pot? Here's a picture of it. The new growths are too small to be visible on the picture, but they grow from the base if this growth. It's a bit dark already so perhaps the quality is not too good.
Attachment 72453

This is what makes orchids such amazing things. Plants, and to a larger extent anything that lives, has the ability to multitask if the conditions are present for it to do so. Many functions in life, in terms of growing or breeding etc, are started after something triggers it. In the case of our beloved orchids, if the condition exists to cause it to flower, but the condition also exists for it to grow a new bulb or new roots, then it'll do so. These triggers at often chemical in nature, and so long as the plants environment provides the components for it to complete the cycle, it'll do so. You can even argue that even if the components aren't there to complete a cycle, it'll still attempt it. How often have you had a stalled spike, or leaf etc?