My view in the following is biased because I honestly believe I was not performing as bad as to be sacked during the 6-months probation period. The evidence is that after Wayfair I found another job with 20% more pay in 3 three months. If you do not fundamentally agree with me on this please do not respond or take my advice seriously.
1. Some boss in EU marketing team do not appreciate their subordinate's work. To him/her, you are a variable that needs to be entered into his/her fotmula to get the result he/her wants.
2. The team atmosphere is made unpleasant by this practice and expectation. I know some colleagues contantly work over time without being paid and are too afraid(or unwilling) to leave their slack/email idle on paid vacation/sick leave.
3. Your hiring manager has a direct say on your performance. They would have claimed to help you "grow" if your performance are not good enough. They would also tell you “Wayfair has very competitive culture and the best ones get a 'average' review meaning that they 'meet' expectations. What left unsaid is that if, you are not obedient enough, or not 'performing' enough in his/her eyes, you will be rated as less than 'average' and the consequence is that you don't get the bonus that they are trying to promote to you at the offer stage or even get sacked.
4. Do not trust HR in this company. I mean some are really nice during interview. But in my experience, the one who appeared at the meeting with me and my manager, delivering the message that I was sacked, was the same person I made compaint to about my hiring mangeer when I was still in the company :).