https://www.trustpilot.com/review/bitpie.com
https://www.trustpilot.com/review/mathwallet.com
https://www.trustpilot.com/review/mathwallet.org
I do not know the Math wallet that you are talking about but there is no review in one and only one review in the second. About Bitpie, no review at all. Do not use a wallet that people are not using.
Review onTrustPilot does not mean at times that the wallet is good but about the ones you listed, people are not using it, do not use it. Use the official wallet of the coin if you do not find another wallet for it yet. Be careful not to be scammed, there is always many new altcoin scam.
I have personally used math wallets without any negative consequences. It's almost like a trust wallet where you can access your crypto wallet through a privet key, mnemonic phrase. The only difference I see is math wallet supports more blockchain than the trust wallet.