Yes because they have to bring it all back up in phases so that they only face the load spike* from one interconnect at a time, which can take some time and can fail if there’s unknown damage like the GP said.

It really depends on the region though because almost all large hydroelectric dams are designed to be primary black-start sources to restore interconnects and get other power plants back up quickly in phase with the dam. i.e. in the US 40% of the country has them so it’s relatively easy to do. The hardest part is usually the messy human coordination bit because none of this stuff is automated (or possible even automatable).

* the load spike from everyone’s motors and compressors booting up at the same time

Spain is but Portugal is only connected to Spain and they are currently doing a full black start.

For Spain the external power and synchronization can come from France rather than generators which will help, but the process and complexities are still mostly the same. Call it a dark start, perhaps.

Presumably not

> A black start is the process of restoring an electric power station, a part of an electric grid or an industrial plant, to operation without relying on the external electric power transmission network to recover from a total or partial shutdown.[1]

https://en.wikipedia.org/wiki/Black_start

Yup - a true black start would be substantially more difficult and time consuming. More like a gradual reconnect.

Then again they might be less prepared precise because of the euro grid is available

It's a complex enough issue that you can't really 'hand wavey' it. The details are specific and thorny.