Why does PreTrainedTokenizerFast return a list instead of tokenizers.Encoding instance?

from transformers import AutoTokenizer
from tokenizers import Tokenizer
from tokenizers.models import BPE, WordPiece
from tokenizers.trainers import BpeTrainer, WordPieceTrainer
from tokenizers.pre_tokenizers import Whitespace
tokenizer = Tokenizer(WordPiece(unk_token="[UNK]"))
trainer = WordPieceTrainer(vocab_size=5000, 
                           special_tokens=["[UNK]", "[CLS]", "[SEP]", "[PAD]", "[MASK]"])
tokenizer.pre_tokenizer = Whitespace()
tokenizer.train_from_iterator(texts, trainer)
output = tokenizer.encode("Hello, y'all! How are you 😁 ?")
tokenizer1 = AutoTokenizer.from_pretrained("bert-base-cased")
output = tokenizer1.encode("Hello, y'all! How are you 😁 ?")

<class ‘tokenizers.Encoding’>
<class ‘list’>

Isn’t it supposed to be the same object?

Also, how do I get tokens from pretrained AutoTokenizer?

Thank you!

I think I found an answer in one of the tutorial videos. I should use tokenizer.beckend_tokenizer that is an instance of tokenizers.Tokenizer class.