Agreed, the pictured out-of-round guides need to be either lined using a bronze K Line (my preferred method for B/RB heads when retaining the 3/8" valves) or new bronze or spiral iron guides installed when using 11/32" or 5/16" valves.

The hand drill K-Line reamer like the video above is used as a rough early step in the process to ream the original guide large enough to press in the guide liner before the precision step of broaching the liner to the desired valve clearance, and a quality machinist will use the bit not in a hand drill but on a sliding table drill press or the like to stay away from the kind of wobbling seen in the video and to ensure every guide is reamed exactly perpendicular to the rocker towers. That reamer is not designed and won't work properly to resurface existing guides that are worn out of round, especially with a hand drill and with worn seats that may throw off the bushing alignment. Using the hand drill reamer to finish the guide will likely lead to multiple valve train issues including burned valves due to improper seal, premature valve and liner wear due to slop in the guide and fluctuating rocker tip geometry, and poor and fluctuating rocker tip geometry due to slop in the guide.

Most oversized valve stems went out of production decades ago when machining processes evolved (such as the guide liner) since reaming the guides for larger valve stems requires the same amount of labor as installing guide liners and standard-sized valve stems are less expensive than oversized valve stems.

I assume by "replace" Nathan means removing the old guides and installing new ones. On A/LA/B/RB heads, the old guides are replaced by either reaming them out and lining with K Line bronze inserts or completely machining them out and pressing in new bronze or cast-iron guides, either method then being finished to the desired valve clearance. My machinist charges $38 for the sixteen guides and $150 labor to install them--this is at $110 USD shop rate. It costs additional to have him cut the guides for positive seals. This work doesn't include the valve job, which the photos above show the heads need a valve job an might need new valves depending on the stem wear of the existing valves. Then there's hardened exhaust seats to consider depending on the amount of use the engine will see.