Momma Homles, JMO so take it or leave it

,
sounds as though Ollie is perhaps a bit young to go without a nap--and is getting OT. like you said, he wouldn't normally fall asleep so quickly-the fact that he is falling asleep so quickly likely means he would have/should have napped slightly earlier.
My son is 25months and is LOW on the sleep need requirments but still happily naps. mind you he is in his crib and does not have another sibling yet. I could not imagine him without a nap to be honest.
this is what our day looks like:
wake 6/6:30
nap 6hrs later from wake--so usually 12:30-2
bedroom at 7 for books etc, in to bed typically 5.25hrs after nap ends
asleep 20-30min later--so 7:30 or so
so anywhere from 10.5-11hrs at night and 1.5hrs at nap.
could you try the nap a bit earlier and see what happens?--lay down with him whatever just to get him to nap?