Often but not always. I worked as a senior exec in a near-FAANG, large public corp and at one point the board changed the equity comp of my level and up execs to a pretty complex formula that was significantly back-ended but also had possible multipliers in the event our stock metrics exceeded the avg stock metrics of a composite of several similar firms in similar markets. At the time it was started, a lot of us assumed we might get about the same at the end of the day and maybe a little more but have to wait longer for it.

After four years, we actually maxed all the multipliers and ended up making >200% what we would have under the previous standard vesting. I heard that HR and the board comp committee felt they'd made a 'mistake' because we'd ended up getting so much more than the 'intended' range - however, we also worked our asses off and the companies stock was soaring, so they couldn't really complain. BTW, the net-effect of the back-loaded vesting and soaring stock was that we all ended up holding for longer than we otherwise might have which ended up adding nearly another 100%. Since we're already talking about pretty hefty comp numbers, post-multipliers plus a ~doubling of the stock price, it ended up being life-changing money. Good times, indeed.

So, not every 'non-standard' equity vesting schedule is necessarily a bad thing. Sometimes they are structured as a set of trade-offs, where the downsides are balanced by upsides tied to certain things and need to be assessed on that basis.