Are Polonium and Astatine metalloids because they touch the “staircase”…

Are Polonium and Astatine metalloids because they touch the “staircase”…
Depending upon which periodic table you look at, you will see polonium and astatine listed as metalloids. Typically, “anything touching the zig-zag ‘stair-step’ is a metalloid” is a general rule, but research evidence better lists polonium as metal and astatine as a halogen. And we already know that Aluminum is a metal, even though it is touching the staircase.
While the ‘stair-step’ is a useful mnemonic device that adequately captures the metalloids, it also includes some elements that do not belong in this category. A key example is aluminum, which is located along the ‘stair-step.’ Yet there is extensive agreement that aluminum should be classified as a metal because of its many metallic properties. Now, polonium and astatine do not fit into the mnemonic device either.
The distinction between metal, metalloid, and non-metal is not as clear-cut as might seem. Many elements (including hydrogen itself) have different allotropes that fall into different categories, depending upon their temperature and the pressure applied. For this reason, scientists rarely rely on these categorizations (metal, non-metal, or metalloid) as absolutes.
Given research, it is clear that polonium should be classified as a metal and astatine as a halogen. Of course, the distinction is not of much practical use for either element, given that only small quantities are available of each and both are unstable isotopes (nuclear decay).
The Evidence:

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  The trend toward greater metallic character of the elements [within group 16] is complete at polonium [Po], which has two allotropes, both with typically metallic structures: a cubic, converting at 36°C to a [beta] rhombohedral (mp 254°C). Each of these has resistivity typical of a true metal with a positive temperature coefficient.” --Cotton and Wilkinson
  
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  “Because of its [polonium’s] short half-life (138.38 d) this entails a tremendous energy output of ~ 140 W per gram of metal…” --Greenwood and Earnshaw
  
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  “Both [allotropes of polonium] are silvery-white metallic crystals with substantially higher electrical conductivity than Te.” --Greenwood and Earnshaw
  
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  “The trend to metallic conductivity is also noteworthy; indeed, Po [polonium] resembles its horizontal neighbours Bi, Pb, and Tl not only in this, but in its moderately high density and low melting point and boiling point.” --Greenwood and Earnshaw
  
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  “Our knowledge of the chemistry of At [astatine] is based mainly on tracer studies which show that it behaves about as one might expect by extrapolation from the other halogens.” --Cotton and Wilkinson
  
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  “The name [halogen] has since been extended to cover all five members of Group VIIB of the periodic table.” [F, Cl, Br, I, and At.] --Greenwood and Earnshaw
  
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  “Three oxidation states of At [astatine] have been definitely established (-I, 0, V) and two others have been tentatively identified [+I (or III?) and VII]…These values should be compared with those for the other halogens (in 1 M acid) [halogens have oxidation states of the following in 1 M acid: -I, 0, +I, III (Cl only), V, VII).].” --Greenwood and Earnshaw