For now it is the standard behavior indeed (I think it should be changed, but that’s a different story, no need to open that debate again). The implicit typing is a great example, the absolute vast majority (if not all) Fortran programmers do not use implicit typing, they always use “implicit none”. There is a significant subset of Fortran programmers who want standard conformance by default, and since the standard says implicit typing by default, they are willing to live with it.
LFortran isn’t a production compiler yet, so it remains to be seen how programmers will like their nonstandard choices.
Indeed.
We plan to add -std=f23 option that will make everything strictly standards conforming. We can add more info into error messages if it is confusing.