It doesnt really matter !!!! Tayana 37 decks are NOT (usually) built over large slabs of substrate but are set over approximately 4 to 6 " squares of encapsulated wood substrate, each set being an independent core and bounded by polyester. Most times if water penetrated, the amount on wetness will only be in the individual 4x4 or 6x6 core not a whole zone of deck. What should be done is to remove a representative amount of screws and actually probe (dentist pick etc.) into the core, the probe will come back out with amounts of rotted material, then recaluclate the amount that had rot vs. those that didn''t for an overall approximation of total wetness. Delamination even if wet does not seem to be a problem on Tayanas because of the small voids (4x4 or 6x6) containing the underlayment / core sections. Because of the very heavy construction, and independent cores, it will probably be impossible to ascertain with a moisture meter (either from the top side or bottom side) what the condition of the overall deck will be; the only way I perceive to ascertain deck wetness on a Tayana is by direct and actual probing - removing some screws and actualy probing. Some T37 owners aggressively replace the wet teak decks with a total reconstruction, others simply ignore it because of the ''latent'' strength due to the ''boxing'' of the core.
More realistically, if 60% of the plugs are missing, it would in a practical sense, mean that the teak deck is thin and worn out... and probably needs a total replacement or conversion to a teakless deck.... and that is going to cost some major $$$ to restore or a LOT of sweat equity on your part to restore.
Other: On a Tayana also be sure to carefully inspect for rot in the bowsprit, especially (and most difficultly) from the underside where the sprit is penetrated by throughbolts and by removing the stainless ''anchor guards'' and actually inspecting. The sprit is laminated alternatively with teak and asian (poor) grades of mahogany - the mahogany being very subject to rot. Also carefully look at the
rigging fittings for signs of metal fatigue - especially the cranse collar on the bowsprit. Wetness problems can be a bigger problem at chainplates and mid station stancheon bases.... easily visualized underneath by discoloration at the nuts, and backing plates etc. that hold the stancheons, etc. Make it a requirement of your surveyor to remove the panels that enclose the chainplate bases and actually visualize for rot and metal degradation.... make it a requirement. Also make it a requirement to open a few areas to inspect the watertight quality of the bulwarks - from underneath.
Hope this helps.