It does seem wierd that the email would come so last minute, but there's probably a lot of reasons it could have happened...
In my process I definitely had times when the system from PC sent out emails way after they should have gone out. Things reflected in the portal (especially MAP) that I didn't get notified for for a few days. It could also just be that she has times she (or he) is trying to fill and/or had cancellations last minute. Also, the holidays and vacation could have impacted when they were able to send the links out.
You might be able to request a simple phone interview rather than a video chat if that makes it easier to work around your work schedule?? My interview ended up just being a voice interview.
Whatever the case, its good practice for service
All kinds of last minute (or no minute) changes to things....especially during PST!
As for being at a disadvantage, definitely don't put that on yourself. The PC interview is relatively laid back as far as job interviews go, and, depending on your PO, can actually end up being a lot like a structured conversation more than a formal, stressful interview. In fact, many POs (and RPCVs in general!) like to talk about their experiences during the conversation! I know its much easier to say than do, but this is one interview that just relaxing and being yourself is honestly great advice for. YMMV, obviously.
Once you get things scheduled, it will not be held against you at all if the original times don't work out. I actually had my interview pushed back twice - once on me, and once on them!
Hope it works out, and good luck!!