I think the observance in Indianapolis of Lesser Yellowlegs in late June is perfectly normal. Records show, that on the upper Texas coast in the last week of June and the first week of July they go from rare to uncommon. They become common for the middle two weeks of July, then abundant the last week of July through mid September. A number of other species are being seen now on the upper Texas coast.
In my opinion, the timing of migration for birds doesn't change much from year to year. We are seeing big shifts in the ranges of some species these days but not timing. We do see earlier fall dates and earlier spring dates each year. I think that is a Patagonia effect rather than an actual shift in migration timing. Without going into the long story of Patagonia, that means that with so many more birders in the field than in years past, we should expect to see more birds in places and at times not previously expected. All that because we are discovering things that have occur ed in the past but were just not seen.