Inconsistency in isEqual methods

[Yeti-or]

https://runkit.com/yeti-or/bem-entity-vc-cell

const BE = require('@bem/entity-name');
const BC = require('@bem/cell');

const button_disabled = BE.create({block: 'button', modName: 'disabled'});
const b_d = BC.create(button_disabled);

console.log(button_disabled.isEqual(b_d)); // is this okay? I think yes
console.log(b_d.isEqual(button_disabled)); // but then why this throws?