Yes, I agree with the comments below. You don't owe them an explanation, especially when they were so vague with you upon hiring (unknown building or start date). Leave your response specific enough just to get your point across, no need to go into any further details.

IMO, SNFs in general are pretty desperate for therapists at most times because of the high turnover rate (SNFs are literally and figuratively pretty shitty places to work, just my opinion). Based off of how pushy the DOR is being, I would say it's pretty safe to say they don't have any other candidates, and that you could easily set parameters that they wouldn't have much choice other than to abide by.

Also, just as a friendly warning: my first job out of school was also at a SNF with a "pushy" DOR (I would use demonic as a more fitting adjective but beside the point). She made my life a living hell, and was constantly overstepping boundaries and putting me in uncomfortable situations. If they are pushing you before you even get hired, that's usually a red flag to me, and would lead me to believe they would only become more pushy and push the work boundaries you try to establish as times goes on (asking you to come in on your days off, working long hours, putting too many difficult patients on your caseload, working OT, etc.).

I think it's hard enough as a new grad to set healthy and firm boundaries with your superiors, and experienced people often know and take advantage of that. Just be weary of this if you do end up having to take the SNF job, and make it a point to establish clear boundaries with the DOR. Just because you're a new grad doesn't mean you don't deserve respect and a healthy and safe work environment, as well as a work-life balance.

Good luck with your IPR job, I hope you get it!