No.

- Importing a private key will import only one address.
- Importing a seed, will import an entire chain of addresses, generated from the seed, using the given Derivation Path.

I'm not sure what you mean by "or it is also applicable from electrum > other wallets?"... are you asking of you can move an Electrum seed to other wallets? If so, the answer is no... Electrum does not use BIP39 compatible seeds like most other wallets. However, Electrum can import BIP39 compatible seeds from other wallets...

so in summary:

Import Private Key is not the same as Import seed.

Electrum seed -> Other Wallet = Not Possible
Other wallet seed -> Electrum = Possible