Is it strange for a D3 coach to give you slot and tell you you have slot whether you apply ED1, Ed2 or RD? That is what happened.

Not so odd. Just make sure you have full coach support regardless of the round of admission. Have you had an academic pre-read?

yes, full support and pre-read

I’ve seen this for D1 also (not ivy) with a recruited full support slot (into a particular school within the uni).

If coach says full support is good for any round of admission, and you had a positive academic pre-read, then there seems to be no reason to doubt what the coach is saying. It’s actually refreshing to see a coach give students more time this year (until RD) to decide what to do.

It happens as you have seen. It depends of course on the school and the sport.
In this case I am assuming that this school has “slots” and not just spots on the team with a coaches recommendation to admissions. Some D3 schools do not have slots per say.
Also, depending on the school and the student, some students may not have any issues getting admitted without the coaches support and they would be good recruit for the team.

It depends. Our experience was that midwestern LACs were more likely not to expect recruits to apply early, and we even had one or two say that applying early was not necessary. You may experience a different response, however, if the coach learns that you have applied somewhere else early.

I also could imagine that happening if a recruit was at the 50-75th percentile for matriculating students at the school, suggesting that the recruit would be competitive for the regular decision pool.

I suspect it is unusual for the D3s that have extremely competitive admission standards.

My senior girl thrower got a yes D1 track and field with just her grades as well. This seems like such an odd year we are just getting started with our top 10 list.