WoS is a custodial wallet, so you are correct to wonder if your funds there are safe. The answer is, ... no, your funds are not safe on a custodial wallet. Because YOU HAVE NO FUNDS on a custodial wallet. You have only an IOU from the operator of said custodial wallet.

That being said, WoS has been in operation from 2018, and the creators of WoS have been a bitcoin service beginning several years before that. So your risk of getting rugged because of unscrupulous operators is not high, in my opinion. And hopefully they know how to secure customer funds properly (hot wallet only for what is need for daily operation, and cold wallet with multisug, etc.)

But would I store any funds of significance on WoS? Absolutely not! I do use WoS but have never had a balance on it about maybe 50,000 sats (~$20 at the time). I would have no worry using WoS maybe for a RoboSats trade for an amount of a couple hundred dollars, ... just that such an opportunity has not yet arisen. (WoS is one of the few wallets that handle an LN "hold transaction", which is a requirement for using RoboSats). But I wouldn't leave those funds on WoS after the trade very long after the has completed. I would do the same whether this was WoS or any custodial exchange or wallet.

One potential risk is how WoS is based out of Australia. It would not shock me that one day I will wake up and see an e-mail from them stating that my account on WoS is locked until I KYC myself. I doubt WoS would want to engage in "shotgun KYC" like that, but when you have an anti-bitcoin, tyrannical government like Australia is now, be prepared for something like that to happen.

WOS is great for showing people how LN works and getting them started, if you have a few bucks in it that you won't cry if its gone, then WOS is your wallet of choice.

I personally wouldn't trust it for more than 50 bucks, any more I'd keep in a non-custodial LN wallet where I can close the channel