Yes Standby boats are still required in most places and in the North Sea they have become very sophisticated, with very specific rules and requirements to obtain REC-Class.
Here is a modern EERV for the North Sea:
http://www.northstarshipping.co.uk/our-fleet/grampian-contender
The biggest fleet of EERVs belongs to Esvagt:
https://www.esvagt.com/fleet/fleet-overview/
But that does not mean that normal LSA can be dispensed with on the rigs and platforms.
It used to be just about any old thing that will float would do as the standby boat. Sometime they didn’t even have enough space to accommodate the number of people on the rig/platform they are assigned to, paying lip service to the rules and requirement and disregarding safety of personnel.
Mobile rigs have been required to carry lifeboats since sometime in the early 1980’s, incl. US flag rigs regardless of where they were working, at least outside US waters.
PS> There are still some converted fishing boats in use as Guard boats for seismic operations around the world: https://www.gm-ships.com/vessels/