timing footclient -e true is not actually measuring what you think its measuring. It's measuring the time it takes to open a socket and write a few bytes to it. Not the time it takes to run true in a new window and then close it. And just FYI both alacritty and kitty have server/client modes too. foot without server client mode does indeed startup faster than any GPU based terminal emulator because GPU based terminal emulators have to probe the GPU card(s) ont he system for their capabilities which is approx 100ms of unavoidable delay until someone convinces the kernel developers to cache this data.

In client server mode all of foot/alacritty/kitty/urxvt will open windows in a few ms.