I can't comment on FBSL, as I have never used it.
However, the idea that there is a BASIC standard is a pipe dream. Every variant seems to implement their own unique syntax changes, which is part of what makes each variant special in its own way. There would be no need for so many variants if they were all identical. Even in the heyday of BASIC, in the 70s-80s, each system had a unique BASIC and you often had to tweak code to get it to run on a different system. Much like Microsoft's bastardization of C++ in VisualC++/VisualStudio. If you use it, you will have issues working with other C++ compilers. At least with C++, there is a semblance of a standard. BASIC, has always been no-holds barred when it comes to syntax. Even Bob Zale destroyed the legacy of PowerBASIC by introducing OOP/COM and trying to make PB a C++ wannabe language in an effort to retain users who were leaving for compilers that better supported modern versions of Windows. Bob was not alone as there were many BASIC/C/C++ Hybrid languages. Some good, some bad. Few got the hybridization "right". Bob missed it by a mile.
Coding standards have changed since the 70s and 80s. Even leaving out OOP, what may have been acceptable as a standard even in the 90s is not acceptable now. There is no right or wrong answer, each language needs to use what works best for them and their demographic. If you are targeting legacy systems, legacy standards from the 70s and 80s would be ideal. If you are targeting the 21st century, then it is best to forget the "perceived" standards of the old days.
If you don't like what Oxygen offers, don't use it. Problem solved.